BOYNTON BEACH, Fla. — Scot Peterson had spent much of the past three months in hiding, but now somebody was walking onto his porch and toward the front door. A motion detector activated an alarm inside his duplex. Peterson, 55, ducked away from the windows and bent out of sight. His girlfriend, Lydia Rodriguez, walked to the entryway and began to pull down a corner of the white sheet that now covered most of their front door. “Oh please,” she said. “What now?”

It had been exactly 90 days since Peterson’s last shift as a school resource officer in Parkland, Florida, where he had been armed and on duty as 17 people were killed and 17 more were injured, and ever since then a procession had been making its way to his door to demand accountability for another American mass shooting. First came the Broward County Sheriff’s Office to repossess his police cruiser and his badge. Then came dozens of reporters and television trucks, jamming into the cul-de-sac of a retirement community to broadcast stories about the “Coward of Broward.” Then came a court officer serving Peterson with a lawsuit from a parent whose daughter had been fatally shot on the school’s third floor. “Scot Peterson is a coward,” it read. “Scot Peterson did nothing. Scot Peterson waited and listened to the din of screams of teachers and students, many of who were dead and dying. He let innocent people die.”

“I’m not here,” Peterson said now to Rodriguez as she looked out beyond the sheet and sunlight streamed into their living room.

“It’s OK,” she said, waving at two octogenarians holding a bag of cookies on the porch. “It’s the neighbors. Jim and Kelly.”

Peterson invited them inside and offered them seats in the living room. Christian music played over the speakers and Fox News Channel was muted on television. “Thank God for you two,” Peterson told them. They were two of the only people who had come over after the shooting just to ask if he was OK. As the crowds grew outside his house, they had let him sneak out his back door and through their yard whenever he left to see his lawyer, visit a psychologist, or go for a drive when he couldn’t sleep.

“How are you managing?” Kelly asked.

“I have some OK moments,” he said.

“We’ve been worried,” Jim said. “We’ve been watching the news.”

“Oh yeah? What are they saying?” Peterson asked, even though he had already heard what they were saying and couldn’t stop himself from hearing it, even now. “A disgrace,” the sheriff had said during a news conference. “An awful human being,” one survivor said on national television. “A blight on law enforcement,” said a police union. “A coward,” said President Donald Trump. “When it came time to get in there and do something, he didn’t have the courage.”

Their words ran in a loop through his head, because all this time Peterson had been wondering, too: What more could he possibly have done? Why had he failed to save so many lives in the exact scenario he had spent so much of his career training for – to find and kill an active shooter? He had worked as a sheriff’s deputy for 32 years, as a school resource officer for 28, and at Marjory Stoneman Douglas High School for nearly a decade. He was the lone deputy stationed at the school, sworn to serve and protect a community of students who called him “Dep,” honored him with awards, and invited him to proms and football games. He had been admired and maybe even beloved up until a former student named Nikolas Cruz allegedly arrived at school with an AR-15, and ever since Peterson had been living inside those next seven minutes. He had briefly considered changing his name or moving out of state, but even if he could somehow outrun infamy and embarrassment, he had decided there was no escape from the questions and doubts that consumed him.

“It’s haunting,” Peterson said now. “I’ve cut that day up a thousand ways with a million different what-if scenarios, but the bottom line is I was there to protect, and I lost seventeen.”

“Come on now,” Jim said. “It’s not all on you.”

“But that’s the perception,” Peterson said. “You’re a hero or a coward, and that’s it.”

“People are looking for someone to point to and blame,” Jim said. “They’re just trying to make sense of it.”

“I know,” Peterson said. “So am I.”

• • •

It was in some ways the most simple kind of crime to solve: committed by one perpetrator who had surrendered and then confessed within an hour, and yet months later half a dozen inquiries remained underway, each an attempt to derive sense and order from seven chaotic minutes. The FBI was reviewing its threat response. A governor’s commission was examining school security failures. The sheriff’s office was looking into radio malfunctions. The Florida Department of Law Enforcement was investigating the sheriff’s office.

Peterson had been doing his own investigating, too, studying dozens of pages of documents inside his duplex. He’d re-watched surveillance footage and read witness statements, searching for a way to reconcile the deputy he believed he was with the coward who was maligned each day in the national news.

“How can they keep saying I did nothing?” he asked Rodriguez one morning, looking again through the documents on his kitchen table. “I’m getting on the radio to call in the shooting. I’m locking down the school. I’m clearing kids out of the courtyard. They have the video and the call logs. The evidence is sitting right there.”

“It’s easy to second guess when you’re in some conference room, spending months thinking about what you would have done,” Rodriguez said.

“There wasn’t even time to think,” Peterson said. “It just happened and I started reacting.”

He remembered being in his office on the afternoon of Feb. 14 when the first call came in to his school radio, as he was waiting to meet with a parent about a student’s fake driver’s license. On most days, that was his job: to police the small stuff – to chase down stolen cellphones, confiscate marijuana, lecture students for vaping in class, and break up the occasional hallway fight. Twice he had caught students with knives, but not once in the past decade had he encountered a gun. Stoneman Douglas was a high-achieving suburban school, with Audis in the student parking lot and packed PTA meetings each month. The school employed eight security guards to help monitor 13 buildings spread across 45 acres, but Peterson was the only person who carried a gun. “If I have to arrest you, then something has gone wrong,” Peterson often told students, because his role was less to be an enforcer of the law than a friendly reminder of it. He had worked before as a corrections guard and as a road officer arriving at the scenes of fatal car crashes and homicides, but it was his work as a school resource officer that had made him one of the most decorated deputies in Parkland.

“Possible firecracker,” came the call in to his school radio at 2:21 p.m., from one of the school’s eight full-time security guards. “Firecracker over by the 1200 building.”

Peterson had dealt with fireworks on campus before, and if there were ever a likely time for one it was now, during the last class period on Valentine’s Day. “Probably a few kids acting like idiots,” Peterson remembered thinking, and he stood from his desk and walked out to investigate. His office was a few hundred yards from the 1200 building, and he was heading in that direction with a security guard when a fire alarm went off. Smoke from the firecracker had probably triggered the alarm, Peterson remembered thinking. He began running toward the 1200 building until one of the unarmed security guards swung by in a golf cart and offered him a ride. Peterson climbed onto the back and jumped off the cart about 20 yards from the 1200 building. The security guard drove away, and Peterson took a few steps toward the building before he heard two loud bangs. They didn’t sound like firecrackers. Maybe gunshots, he thought.

He remembered being unsure whether the blasts were coming from outside or inside the building, or if someone was firing shots in the adjacent parking lot or sniping from the roof. He didn’t know, and no one was there to tell him, and he remembered reacting in those first seconds by doing what he believed he had been trained to do: taking cover in a tactical position so he could clear the area. He leaned his back against the wall of an adjacent building. He took out his gun and scanned the surrounding palm trees, the courtyard, the windows, the parking lot, and the roof. He waved at students who were walking through the courtyard and told them to clear the area. He reached for his school radio and gave a “Code Red” to lock down the school. He picked up his police radio for the first time just after 2:23 p.m.

“Please advise, we have possible, uh, could be firecrackers. I think we got shots fired. Possible shots fired, 1200 building,” he said, according to a recording of the radio traffic.

He remembered standing for the next several seconds with his back against the wall, scanning the area around the building for a possible shooter. Trees. Roof. Windows. Courtyard. Trees, roof, windows, courtyard. He could see much of campus from his position, but he couldn’t find a shooter. He remembered staying in place because he didn’t want to expose himself when he didn’t know where the shots were coming from. He remembered feeling certain the gunshots were coming from somewhere near or inside the 1200 building, but where?

“Make sure we get some units over here,” he said into the radio, still at 2:23 p.m. “I need to shut down Stoneman Douglas, the intersection.”

“We’re talking about the 1200 building,” he said, a few seconds later.

“We don’t have any description yet,” he said, at 2:24. “We just hear shots, what appear to be shots fired.”

How often had he envisioned this moment? How much time had he spent studying other mass shootings, imaging himself on scene, wondering how he’d react? He’d gone to annual conferences about school shootings, taken a class on confronting active shooters and led annual lockdown trainings for teachers. He had started his career as a school resource officer years before the 1999 shooting at Columbine High School in Colorado, back when the idea of a school shooting seemed far-fetched, but now it was a possibility he carried in his mind as he walked around campus each day. There were always a few students the administration worried about, and three years earlier one had been caught with written plans for how to shoot up the school. Peterson had imagined what he would do if someone started firing in the crowded courtyard during lunch or at halftime of a football game. The ending he imagined was always the same: He identified the shooter. He engaged the shooter. He killed the shooter.

But now he stood against the wall, holding his radio in one hand and his gun in the other. He remembered wondering why he couldn’t locate the shots. Trees, roof, windows, courtyard. The fire alarm was still blaring. Police sirens were closing in from all directions. From Peterson’s position, he could see only the east side entrance to the 1200 building. Meanwhile, on the west side, at least one victim was already down.

Students inside the 1200 building were at that very moment flooding 911 with calls describing the exact location and description of the shooter, but it turned out that those calls were being routed not to the Broward County Sheriff’s Office but instead to the bordering Coral Springs Police Department. Coral Springs officers were not yet on the scene, and even once they arrived, they communicated on a separate radio system from Peterson and the rest of Broward County. The only information being relayed to him was coming out of his Broward County radio, a soundtrack first of silence and then of mounting confusion as the shooting continued into its fourth minute.

“I hear shots fired by the football field!” shouted the second Broward County deputy to arrive. “Shots by the football field.”

“Some thought it was firecrackers. We’re not sure,” said the next deputy on site. “By the football field.”

“We also heard it over by, inside the 1200 building,” Peterson said, still standing in place. “We are locking down the school right now.”

“I got more students running west toward the football field,” another officer said.

“I hear shots fired,” Peterson said. “Shots – ”

“I have a gunshot victim,” said another deputy. “He is by the entrance to West Glades, on the west side of the school.”

“Does he know where the shooter is?” Peterson shouted, but now it was already six minutes into the massacre, and the last victim had already been shot on the third floor. The gunman was dropping his AR-15 near the stairwell and then heading out of the building, blending in with the crowd of frantic students. The shooting Peterson was supposed to stop was already over.

A Coral Springs SWAT team arrived almost five minutes later to clear the building, and Peterson left his position against the wall and ran to give them his set of master keys to the classroom doors. He passed by the entrance of the 1200 building for the first time, and there in the hall he could see two victims. He still didn’t know whether there were more. He still didn’t know anything about the identity or the location of the shooter. He stayed on the scene for the next several hours, helping to move bodies as the death toll mounted, and later that night he went home to Rodriguez. She had been sure he was dead the moment she heard the report of “one victim” on the television news. They had talked dozens of time about how he would be the first person through the door to confront a shooter. But instead, here he was, stammering over his words, the grief and self doubt already beginning as he tried to make sense of why 17 people were dead and 17 were injured and the only dirt on his uniform was from where his back had been pressed against the wall.

“I couldn’t get him,” he remembered telling Rodriguez that day, before anyone else had begun to assign blame. “It was my job, and I didn’t find him.”

• • •

In his sleep he was still looking, still scanning the roof, windows and courtyard, only to awaken each morning to the fresh realization of the same result. He had gone to see a psychologist and a psychiatrist after the shooting, and he had come home with a prescription to help him sleep and also a sheet describing the symptoms he had begun to experience: “Confusion.” “Anxiety.” “Guilt.” “Grief.” “Agitation.” “Obsession.”

“Why didn’t I hear more shots?” he said one morning, sifting again through the manila folder as Rodriguez sat nearby. “It doesn’t make sense. I should have heard them, but I didn’t.”

“Relax,” she said, putting her hand on his.

“I only remember hearing two or three,” he said. “I know there were more, but that’s all I heard.”

“Let it be,” she said, even though she knew that wasn’t possible, because she had heard Peterson turn each detail of the shooting into a self interrogation, a cycle of blame and abdication that could sometimes last all day. Maybe he hadn’t heard more shots because of the fire alarm, or because of his positioning in the courtyard, or because the thick hurricane windows in the 1200 building muffled the . Or maybe it was the explanation his psychologist had offered, about the ways a traumatic experience could affect cognitive function, compressing memories, narrowing focus, clouding vision and distorting sound.

“If I heard more shots, I might have known where to find him,” Peterson said.

“If I knew where he was, I could have gone in.”

“If I’d gone in . . .” he continued, and Rodriguez squeezed his shoulder before he could finish the thought.

“Let’s get some air,” she said. She moved the sheet and looked outside to make sure nobody was there. Then they leashed the dog and walked out into a retirement development of cul-de-sacs, palm trees and rows of identical duplexes. Rodriguez had just retired from teaching, and lately she considered it her job to support Peterson and keep him from “sinking too deep down inside his own head,” she said. He hadn’t eaten or slept for two days after the shooting, sick with what he assumed was survivor’s guilt, even though nobody else had begun to publicly question his response. In those first days, the sheriff’s office had invited him to shake Trump’s hand and be congratulated along with other first responders, but Peterson had chosen to stay home. “Nothing good happened that day,” he remembered telling his supervisor.

He gave his official statement to homicide investigators two days after the massacre, attended two funerals, and used sick days to finish out the first week. He was just preparing to return to work when he got a call from internal affairs eight days after the shooting. The sheriff’s office had reviewed surveillance tapes and watched as Peterson stood against the wall. Sheriff Scott Israel offered him two choices: He could be suspended indefinitely without pay, or he could retire with his full pension, an annual payment of nearly $100,000. Peterson had little money saved, two ex-wives, alimony payments and a mortgage on the duplex he’d bought out of foreclosure with $100 down. He didn’t see it as a choice. He signed his retirement papers, and about an hour later the sheriff called a news conference to release more details about the shooting. The country was demanding an explanation, and for the first time he gave them something or someone to blame.

“One deputy was remiss, dereliction of duty,” Israel said. “And that’s Peterson.”

Rodriguez had tried to cushion all that came next with positivity – with Christian music, prayer and aphorisms framed in every corner of the house. “Rule your mind, or it will rule you,” read one. “Cherish Yourself!” “Create Your Own Happiness!” She had disconnected their TV, booked vacations in the mountains of North Carolina, and covertly texted his old friends from the sheriff’s office, nudging them to reach out and call. But on some days, Peterson still seemed unreachable, including now, back on his tablet as he scanned recent headlines.

“Cowardly cop gets princely pension,” read one, and he groaned and flipped along.

“Parkland Parent: ‘Peterson is the lowest form of life.’ ”

“When does it end?” Peterson said, eyes still on the screen.

“Where are you? Come back,” Rodriguez said, but Peterson didn’t seem to hear her. He looked at the tablet, where a little while later he saw a new headline, a breaking news alert. “School shooting in Texas,” it read. “Several dead.”

“Dear God. Not again,” he said, and he turned off the Christian music and flipped on the television in time to see an areal view of Santa Fe High School surrounded by helicopters, ambulances and police cars. Frantic students ran in every direction. A confused parent stammered through an interview. “My daughter. Where’s my daughter?” she said.

“I really shouldn’t watch this,” Peterson said, his voice beginning to crack, but he kept his eyes on the screen. He watched them load the ambulances. He watched a SWAT team enter the school. He watched as the sheriff held his first news conference, promising “accountability and answers.” He watched as a somber news anchor came on screen to confirm 10 dead and several more wounded, including a school resource officer in critical condition.

“Unlike in Parkland, this time the deputy went in,” the anchor said, and Peterson braced to hear his name.

“A case study in the difference between heroism and cowardice,” the anchor said, and now Peterson was shrinking deeper into the couch and into his head.

He had read that the gunman fired more than 150 rounds. Why had he heard only two or three?

“We all remember how in that case the deputy just waited outside, knowing full well . . . ” the anchor began to say, but before he could finish, Peterson reached for the remote and turned it off.

• • •

It was true that he had never gone into the 1200 building that day, neither during the shooting nor after, and now the closest he could come was by watching a video he’d found while looking for information about the shooting on his computer. It was a schematic animation of the crime scene that investigators had made using surveillance footage from 15 cameras in the school. “A little like Pac-Man,” was how one investigator had described the animation, because the 1200 building had been turned into a 3-D architectural sketch, the gunman was represented by a roving black rifle and the students had become colored dots.

It was a version of a mass shooting with no gunfire, no blood, no screaming, no shattering glass and no hallways obscured by smoke. Here, the chaos had been rendered into something silent and orderly, time-stamped to the one-hundredth of a second. Peterson enlarged the video on his screen and hit play.

“As people are injured, their green dots will become yellow,” the narrator said. “Fatalities will turn gray.”

“Oh, not the dots,” Rodriguez called out from the kitchen, because she had watched the video with Peterson once and thought that was probably enough.

“It helps me if I can see it,” he said. “It clears up my thinking.”

So Peterson watched as the black rifle that represented Cruz entered the building on the first floor at 2:21:23 p.m., and he watched seven seconds later as the first two dots turned gray in the main corridor. Within 20 seconds, two more students were dead and four more were injured. Within 80 seconds, a total of eight were dead and 11 injured. “That first burst of gunfire is probably what triggered the firecracker call on the school radio and then the fire alarm,” Peterson said as he watched dots scatter across the scene. “I’m still running out of my office. I haven’t even gotten over there. What am I supposed to do?”

He watched as the black rifle stopped at four classrooms on the first floor, shooting through doors and windows, circling back to fire more rounds at injured victims as dots turned from green to yellow to gray. A green dot entered the hall from outside and came into the corridor, moving purposefully toward the shooter.

“Oh, God. That’s Chris,” Peterson said, meaning his friend Chris Hixon, one of the school’s security guards who had run into the building despite being unarmed. Peterson wondered whether Hixon, who also was the school’s athletic director, had gone in expecting to find a few kids with firecrackers, or whether he had somehow figured out a shooting was underway. “Was he trying to stop it? Was he hoping to tackle him?” Peterson said, but now he watched as the black rifle turned in Hixon’s direction, and his dot turned yellow as he was hit for the first time. The yellow dot raced behind a wall for cover. The black gun moved closer, taking its time, until it and the yellow dot were side by side. “A damn monster,” Peterson said, backing away from the screen as Hixon’s dot went from yellow to gray. Eleven dead and 13 injured in less than two minutes. The black rifle began up the stairs toward the second floor at 2:23:28, about the same time Peterson called in to the police radio to report possible fireworks or gunshots at the school.

“Now I’m finally getting near there,” Peterson said, as he watched the black rifle move methodically through the second floor, finding no victims but firing rounds that traveled through doors and then out windows.

“I was trying to figure it out,” Peterson said again. “I was scanning for the shooter, looking over the windows, the sidewalk, the rooftop. I thought maybe it was a sniper like in Las Vegas. I just didn’t know.”

Peterson watched on screen as the black rifle continued unabated up the stairs to the third floor, arriving on the landing at 2:24:30. The hall was crowded with students evacuating because of the fire alarm. Some would later tell investigators that they didn’t realize an active shooter was in the building. Like Peterson, they hadn’t been able to hear or place the gunshots that were coming from the first floor. Dozens of them sprinted for the stairs as the gunman opened fire, reloading as he traveled up and down the hall, killing six more students and injuring four before he shot his last victim at 2:25:19.

“I was right outside,” Peterson said, pausing the video, rewinding it, sitting again through those 49 seconds when he was standing against a wall and the gunman was shooting on the third floor. On the screen, the shooting appeared clear and the tactical response seemed obvious. Peterson traced his finger over the stairs. “I could have come in over here,” he said. “I could have got him while he was reloading. If I’d just heard more shots, maybe I would have known where they were coming from.”

Maybe then, he said, 49 seconds would have been enough to do something. Maybe, he said, he would have left the wall and sprinted into the building. Maybe, he said, he would have known to run directly to the third floor, rather than clearing the first two floors. Maybe, he said, he would have located the shooter through the dust and smoke and fleeing students. Maybe, he said, he would have harnessed 20 years of training and steadied his gun on the target. Maybe, he said, his Glock would have proved enough to outgun an AR-15.

“It was all so fast,” he said. “I couldn’t piece it all together.”

“Stop torturing yourself,” Rodriguez said.

“It’s brutal,” he said, but he watched until the last dot turned gray and the black rifle moved down the stairs and out of the school.

• • •

He didn’t want to answer his phone. He didn’t want to take the sheet off the front door, leave the house, or risk being seen, so instead he was back on his tablet one morning when a message arrived from another former school resource officer in Parkland, offering a time to meet for breakfast. “Go,” Rodriguez told Peterson, so he chose a diner in Boca Raton where no one would recognize him. He drove 30 minutes and then sat down in a booth across from Frank Wear.

“Convenient spot,” Wear teased.

“I can’t go back into Broward,” Peterson said. “I don’t want to run into anyone. I just – I don’t even know what I would say.”

“No, I get it,” Wear said, because they had been friends for more than a decade. They had gone together to active-shooter trainings and taken a motorcycle trip to celebrate Wear’s retirement in 2017. Wear knew Peterson as a good cop, thorough and fair. “He had a pulse on everything happening over at Douglas,” Wear said, and that had also included Nikolas Cruz. Peterson had met with Cruz in the fall of 2016 and warned him against carrying a backpack decorated with Nazi insignia and racial slurs. He had requested a mental health evaluation after a classmate said that Cruz allegedly drank gasoline. He had even suggested that counselors use Florida’s Baker Act to have Cruz involuntarily committed, but a health expert wrote that Cruz “did not meet criteria for further assessment.” So instead Cruz had left school and Peterson had gone back to dealing with a dozen other troubled students until a year later, when Cruz suddenly returned.

“The thing I keep coming back to is all those shots,” Peterson said now. “I heard two or three. It’s like my focus narrowed and maybe parts got cloudy.”

“I’ve been there,” Wear said, and he began to tell the story of a time when he had been the first officer to arrive at a scene, back in 2001. He had caught two men in the middle of an armed robbery in Deerfield Beach and chased them through the neighborhood by car, eventually ramming his cruiser into their vehicle. The men wore “Scream” masks and carried machine guns, and one fired at Wear as he took cover and shot back. He remembered his heart beating in his ears. He remembered the hazy feeling of time passing in slow motion as he killed one assailant and then helped apprehend the other.

“Talk about performing under pressure,” Peterson said. “Your life was on the line.”

“I just reacted,” Wear said.

“Still,” Peterson said. “It was heroic.”

“I feel stupid talking about this,” Wear said. He shifted in his seat and looked down at his coffee. On a television in the far corner of the restaurant, the news replayed images from the school shooting in Texas. An ambulance raced onto the school track. A team of police officers rushed into the building. Peterson sat in silence for a few seconds and moved the eggs around on his plate.

“Look, you were one guy, and you had communications failures, no information, just chaos,” Wear said. “We’re not all Rambo.”

“They keep saying I did nothing,” Peterson said. “A coward.”

And now he was retreating back into his head, returning again to the wall outside the 1200 building as his food went cold and the wait staff switched over from breakfast to lunch. “I was looking for him,” he said, scanning again over the courtyard, the windows and the rooftop in his mind, trying and failing to make sense out of another mass shooting.

“I just didn’t know,” he said. “Why didn’t I know to go in?”