A black shadow appeared in one of the classroom doors and a plume of fire erupted from the tip of a rifle-like weapon. Mr. Reiss felt a bullet go through his arm, severing a chunk of flesh and bone. Then the gunman turned on the children. The rampage was so brutal and so quick, the teacher said, that he didn’t hear a whimper from them as their bodies were shredded. Mr. Reiss lay in a pool of his own blood for what seemed like an eternity until he heard police gather in the hallway just outside the classroom door. His disciples lay silent, dead or dying. some other children in an adjacent classroom were still alive, faintly calling for help. The police will come and rescue us at any moment, he told himself. But the minutes passed and no salvation came. About half an hour later, the gunman, sitting near where Mr. Reyes was sprawled on the floor, appeared to be taunting him. He leveled his gun at the teacher’s back and fired again. “I think about it more and more. What could they have done differently?’ Mr. Reyes said in an interview recounting the events of May 24, when a mass shooting at the school left 19 students and two teachers dead. He described the anguish the victims felt as officers gathered in the hallway delayed entry to the classrooms where the gunman was hiding — waiting about 78 minutes in a delayed response that a preliminary law enforcement investigation said was complicated by a key search and a decision to try to protect the lives of responding officers. “I was waiting for someone to come,” Mr. Reiss said. “But when I didn’t see anyone come in, I thought no one’s coming.” More than a month after the tragedy, as Mr. Reyes tries to recover from his severe injuries, the memories of that day play over and over in his mind. The day began with a joyous end-of-year awards ceremony, after which nearly half of Mr. Reyes’ 18 fourth-grade students had gone home with their parents. Eleven stayed because they wanted to see the movie “The Addams Family.” “It was supposed to be an easy day, just before the summer holidays,” he recalls. Out of nowhere, Mr. Reiss and his students heard what they now know were gunshots from down the hall. The powerful explosions sprayed debris into his classroom. “There were pieces of wall flying,” he said. The gunman first entered room 112, which was connected to Mr. Reiss’s classroom by another door. He opened fire indiscriminately, police said, fatally wounding two teachers, Irma Garcia and Eva Mireles, and several of their students. Mr. Reis turned to his students. “Okay, we’ve already practiced that. Get under the desks, okay? Just close your eyes and act like you’re sleeping,’” he recalled saying. “I didn’t want them to see anything.” Mr. Reyes does not remember if the gunman entered through the door connecting the two rooms or if he re-entered the hallway. But the next thing he remembers is seeing a ghostly figure wearing a black hoodie over his head and what looked like a black medical mask covering half his face. “I just see that shadow and his eyes,” she said. Then came two sparks from a rifle aimed at him. “He shot me first,” he said. The impact sent a caustic shock to his left arm that felt like hot lava, he said. A large chunk of his forearm was missing. The gunman quickly turned his rifle on the students, unleashing a rain of fire that was so swift and merciless that it was over almost as soon as it began and there was nothing but silence in the room. “They were probably killed instantly,” Mr. Reiss said, although he said some of them may have died during the long wait. Perhaps, he said, they were silent because “they were shocked.” The first officers arrived outside the classroom door about three minutes after the gunman entered the school, according to a preliminary timeline. After the initial attack, Mr. Reiss said, he could hear them talking to each other in the hallway just outside. At one point, he heard one of the officers yell at the gunman: “Come out, we want to talk to you!” The gunman did not respond, although police said two officers were wounded by the graze when he fired a blast into the classroom door. The chatter from the police fell silent. “You didn’t hear anything anymore,” said Mr. Reiss. Most of his students were probably beyond saving, Mr. Reyes said. But at least one child who survived in the next classroom must have heard the police, he said, because he heard someone yelling for help. “Officers, come in,” he heard a small voice say. “We’re in here.” For several minutes, the gunman walked around the room and then perched on the teacher’s desk as Mr. Reiss lay face down on the floor below. In what he believed was an attempt to taunt him – or make sure he was dead – the gunman let a cup of water drip from a desk onto Mr Reiss’ back. The gunman then smeared some of Mr Reyes’ own blood on the teacher’s face and placed the teacher’s phone on his back, which continued to ring as desperate relatives tried to reach him. He appeared to be trying to provoke a reaction, Mr. Reiss said. “He was going to make sure I was dead too. I mean, he had nothing to lose.” About 30 minutes after he entered the room, apparently unsure whether Mr. Reyes might still be alive, the gunman shot him a second time, this time in the back. Mr. Reyes said he became certain at that point that he would not survive. “I won’t make it,” he told himself. “I’m going to bleed.” He then heard the gunman return to room 112. More gunshots were heard. He later heard the gunman close the blinds on an outside-facing window. Mr. Reyes doesn’t remember how much time passed, but suddenly he heard tables sliding and loud footsteps in the next room. More gunshots were heard. Then silence. A man who was part of a Border Patrol team that had breached the order next door and killed the gunman approached Mr. Reiss, urging him to “get up if you can.” When he couldn’t, the agent dragged him out of the carnage by the hem of his pants. “He asked for help to carry me. I was too heavy,” he said, sharing a rare smile. Another agent, he said, suddenly called out an expletive. “There are children down here!” Some of them were still alive in the next classroom. The school was suddenly swarming with police, doctors, ambulances and hysterical parents outside. Mr. Reyes was airlifted to a San Antonio hospital, where he underwent multiple surgeries. Doctors placed a metal plate about six inches into his arm for his wound, covering it with a skin graft from his right leg. A pair of drainage bags are still collecting fluids coming from his lower back and arm. He won’t fully regain movement in the arm, doctors told him. Now he is back in his modest home in Uvalde, a town where he has lived since he was a child. It is decorated with antiques and inspirational inscriptions. “All you need is love,” reads one of them, and: “It takes a big heart to shape small minds.” He dreamed of becoming a lawyer, he said, but 18 years ago he found his calling as an elementary school teacher, the last 10 of them at Robb Elementary. After a difficult year of remote teaching due to the pandemic, Mr. Reyes was happy to see all his students back in the classroom in 2022. “This year was different, I could just feel it,” he said. “They had a close bond. They wanted to know.” When he thinks about the students who died in his class that day, most of them only 10 years old, he finds himself remembering them not in death, but in life. It was Rogelio Torres, who had suddenly become serious about learning his multiplication and division. “He was very ambitious. He wanted to be good at everything.” There was Jose Flores, who lived for lunch and recess and was a “corajudo,” meaning he got upset whenever he didn’t understand a lesson or a math problem. “He was closing and I was telling him, ‘Don’t do that.’ And he did, he learned how to control his frustration.” Josesito, as his family called him, was named on the honor roll for the first time on the day he was killed. And who could forget Jayce Luevanos? He was the popular class clown who reminded Mr. Reyes of the imposing movie character Ace Ventura played by Jim Carrey. Jace liked to wear a t-shirt with a picture of an ice chest that read, “I’m a little cooler than you.” On a recent afternoon, Mr. Reyes sat next to a blue folkloric cross given to him by the mother of Tess Mata, one of the victims, and a block of granite engraved with photographs of all the victims. A cousin, Belinda Aguilera, stopped by to check on him. “He’s doing better, thank God,” Ms. Aguilera said as she studied Mr. Reyes, who sat alone on a sofa. Ms. Aguilera, who lives near the school, said she was one of the people who called Mr. Reyes’ phone in a panic after hearing several gunshots. “You blew my mind because I knew you were there,” she told him, fighting back tears. “I’m so sorry,” he said. “I feel like my phone call made him do this to you.” No, no, said Mr. Reiss, trying to reassure her at a time when almost everyone has lost all sense of certainty. This is none of your business, he said. She didn’t seem convinced. He talked about the long road ahead of him. Not just the healing of wounds – but everything else. “The pain will never go away,” he said.