Teacher fatally shot by his classroom doorway: 'He was trying to crawl back to us'

When a gunman opened fire outside Stephanie Reyna's classroom at Apalachee High School in Georgia , killing math teacher and football coach Richard Aspinwall , she said her classmates jumped into action, shutting and barricading their door.

The chaos began when Reyna, 17, said her class "heard banging on the lockers right outside of the classroom door."

Brayan Maldonado, also 17, said it sounded like someone had been pushed up against a locker.

"My teacher, Coach Aspinwall, he opened the door, and he ran outside to see what’s going on," Reyna told ABC News.

“We heard some popping sounds," Reyna said. "We just stopped, we froze, we didn’t know what was going on. ... So we all ran to the back of the classroom. We hid in the corner."

Reyna said she and her 17 classmates were lying on the ground for several minutes when they heard more popping sounds.

"That’s when we realized that our classroom door was still open," Reyna said.

Maldonado said he started to hear "a little bit of breathing" and "a little bit of groaning."

The students then saw Aspinwall on the ground, they said.

"He was just there, in the doorway, just laying there," Reyna said. "He was trying to crawl back to us ... we just think he was trying to get to us."

"A couple minutes passed by. He’s taking his breaths," Maldonado said. "And then we hear his final breaths."

"Then one of my classmates got the courage to stand up from his position of hiding" and drag Aspinwall's body into their classroom, Maldonado said.

"That encouraged me to stand up," Maldonado said.

He said he and his classmates closed the door and barricaded it with cabinets, desks and chairs.

"We were just putting anything we possibly could to make sure [the shooter] couldn’t get in," Maldonado said.

Once the door was secured, Reyna and Maldonado said they tried to console their classmates.

"Some were hyperventilating, some were crying," Maldonado said. "I was really trying to calm everyone down. Once everyone was calm, I got calm and all the feelings kicked in."

Reyna said first responders evacuated the students to another classroom before they joined the rest of the school at the football field.

Aspinwall, fellow teacher Christina Irimie, and two students were killed in Wednesday morning's shooting in Winder. Nine others were injured.

The 14-year-old suspect, Colt Gray, a student at the school, surrendered at the scene to the school resource officers and was taken into custody, authorities said.

Gray is charged with four counts of felony murder and will be tried as an adult, authorities said. A motive is not known.