UVALDE, Texas -- With summer break just two days away, Tuesday, May 24, 2022, started out as a special one for elementary school students in Uvalde, Texas.
At Robb Elementary, the year-end award ceremony brought together families and loved ones to celebrate student accomplishments that academic year. As the ceremony wound down, some students were taken home by their parents, while others stayed in school.
Alexandria "Lexi" Rubio, 10, received the Citizen's Award from her fourth-grade teacher, Arnie Reyes.
"The Citizen's Award was one that I hadn't expected," said Kimberly Rubio, Lexi's mom, who attended the ceremony. "But that's Lexi. She's just a great person. And I'm glad that her teacher and her peers knew this."
Gloria and Javier Cazares were also in the audience celebrating their daughter Jacklyn "Jackie" Cazares. "This is one of the last pictures that I took of Jackie, and she's with her friends," Gloria Cazares said as she showed ABC News the photo.
Javier Cazares remembered saying goodbye to Jackie after the ceremony. "I blew her a kiss not knowing that was going to be the last," Javier Cazares said.
Later that morning, at 11:33 a.m., an 18-year-old gunman entered the hallways of Robb Elementary carrying an AR-15-style rifle, and devastatingly changed the course of that day.
The massacre claimed the lives of 19 students and two teachers, making it the second-deadliest school shooting in the United States. Survivors and families in Uvalde shared what they experienced on May 24 with ABC News.
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Ten-year-old Caitlyne Gonzales remembered watching a movie alongside her classmates and teacher Mercedes Salas in classroom 106 as the shooting began.
"We were all comfy with our shoes off and then everything happened," Caitlyne Gonzales said.
Mercedes Salas said she heard the sound of gunfire getting closer to her classroom. "The movie was paused, so zero sounds were coming out of my classroom," Salas said. "I went into locking down my classroom just from the sounds."
Teacher Elsa Avila was in classroom 109 when she heard someone in the hallway alerting everyone to get in their rooms.
"I turned off the lights, and I told the kids, 'Let's move! Let's move!" Avila said. "They knew that was the signal that you know we're in lockdown."
Kimberly Rubio, who worked as a reporter at the local newspaper, went straight to work after attending the award ceremony that morning. She heard an alert on the police scanner at her office about a shooting near Robb Elementary.
Kimberly Rubio immediately texted her husband Felix Rubio, then an Uvalde County Sheriff Deputy, who was off duty that day. Felix then turned on his radio to hear what was happening.
"I just hear panic in everybody's voices," Felix Rubio recalled.
ABC News obtained materials from the Texas Department of Public Safety investigative file, including body camera footage and photographs from inside Robb Elementary. This is the first time many of these images and details are being shown publicly.
In interviews with the FBI in the weeks following the shooting, students Khloie Torres and Miah Cerrillo described what they remembered happened in classroom 112.
"Right when he came in, everybody was screaming," 10-year-old Khloie Torres said in the FBI interview. "He said, 'Goodnight,' and he started shooting everybody."
"He tried to shoot at me," 11-year-old Miah Cerillo said in the FBI interview. "I, like, faked that he shot me, and I like, just fell down."
WATCH: Uvalde school shooting survivors tell their stories through photos
Arnie Reyes was in classroom 111, which connects with classroom 112 via interior double doors. He was in the room with eleven of his students.
The gunman shot inside the two adjoining classrooms. Reyes told his students to "close their eyes and get in place."
Reyes was wounded by gunshots to his arm and back. "It was just so, so fast," said Reyes, "and he shot my kids after that.
Teacher Elsa Avila said she was shot in the abdomen while trying to protect her students. Though she was two classrooms away from the gunman, a stray bullet had traveled through walls and struck her. She texted her friend Mercedes Salas.
"My hands were shaking," Salas recalled after reading the text message she received from Avila. "She said, 'Friend, I'm shot. I'm bleeding, help me.'
What Salas said happened next, is something that has been seared in her memory.
"Then we hear screaming. And it was the worst screams I have ever heard," Salas said. Following the screaming, Salas said she heard gunshots - then silence. "And my brain is like "Oh my God, he just killed them. So I heard them die."
Outside the school, parents had descended on the school campus in large numbers after hearing about the shooting.
In body camera footage, a Robb Elementary mom is heard saying, "Nobody understands what we are going through, we are parents! Our kids are in there!"
Miguel Cerillo, Miah's dad, was among the parents outside the school who were growing impatient with law enforcement securing the perimeter. "I said, 'Well, what are y'all doing? Y'all are just standing around,'" Cerrillo said.
Back inside Robb Elementary, almost half an hour had passed and the gunman was still in the building. Khloie Torres made several phone calls to 911 from her teacher's cell phone in classroom 112. In audio released from the 911 calls, she's heard begging law enforcement through whispers to come and rescue her and her classmates.
"Please hurry, there's a lot of dead bodies," Khloie said on the 911 call. "I know how to handle these situations. My dad taught me when I was a little girl. Send help for my teachers. They're still alive, but they're shot."
Miah, who also called 911, and Khloie survived inside classroom 112, where six students and two teachers, Irma Garcia and Eva Mireles, were killed.
Uvalde School District Police Chief Pete Arredondo made the decision to evacuate the other classrooms first. He is heard on police body camera saying, "Time is on our side right now. We're going to have kids in there, but we got to save the lives of the other ones."
Officers eventually broke into classroom windows to evacuate students and teachers. The shooter had yet to be killed.
Families gathered at the local funeral home, across the street from Robb Elementary, to reunite with their loved ones.
"We got up and started running to the funeral home by climbing out of the window," Caitlyne Gonzales said.
Elsa Avila described the glass from her classroom window being smashed by police and officers yelling at the kids to quickly exit.
"After the last student was out, they started to tell me, 'Come on, ma'am. Come on. Let's go.'"
One of the officers had to jump into the classroom to help Elsa, as she couldn't move from the pain of getting shot.
At 12:50 p.m., 77 minutes after the gunman entered Robb Elementary, law enforcement breached classrooms 111 and 112, killing the gunman.
"I finally hear the banging of the chairs," Reyes said. "That's when I said, 'They're here. They're coming in.'"
Felix Rubio watched as first responders rushed children out of the school. He didn't see his daughter Lexi. Some students were being transported in school buses to the local civic center, so he instructed Kimberly to go there.
"My husband does not panic," Kimberly Rubio said, "but he sounded terrified."
At the civic center, Kimberly and Felix Rubio waited for Lexi to arrive off the bus. "I think the longer we waited, the more it became clear that something was wrong," Kimberly Rubio said.
Families were beginning to be notified about the unthinkable news.
"They let us know our baby is gone," Felix Rubio said.
Gloria and Javier Cazares, who were at the school, headed to the hospital after hearing Jackie might be there, and were notified hours later that she was no longer alive.
"I went to my knees and started talking to her," Javier Cazares said. "We were both apologizing for not being able to protect her."
All eleven students who were in classroom 111 at the time of the shooting, including Lexi and Jackie, were killed. Teacher Arnie Reyes was the sole survivor.
"The hard thing for me has been, as a teacher, as an education, you never think about losing a student," Arnie Reyes said. "To lose 11 at a time, at one single time, and then to lose your coworkers that worked right beside you. And then other little kids that were in that class that you knew. It's a lot at once."