Niu Giasolli, a classmate of Castillo’s, said Castillo died after lunging toward one of the shooters, giving his classmates time to escape.

Castillo, 18, was a senior at STEM School Highlands Ranch when he was killed after two students armed with handguns entered the Denver-area school Tuesday afternoon. Eight other students were injured before the suspects were taken into custody.

Kendrick Castillo was identified Wednesday as the student killed during a school shooting in Colorado after he lunged at the gunman.

Kendrick Castillo, 18, was killed after lunging at one of the gunmen yesterday during the school shooting in Colorado. Our children shouldn’t have to stand up to gunmen because too many of our lawmakers are too afraid to stand up to gun lobbyists. Text ACT to 644-33. pic.twitter.com/4BVDNj5GhB

“[The gunman] walked to the other side of the classroom where we also had another door,” Giasolli told the “Today” show. “And he opened the door ― he walked back as if he was going to go back to his seat and then he walked back to the door and he closed it. The next thing I know he’s pulling a gun and he’s telling nobody to move.”

Castillo went after the gunman, Giasolli said.

“That’s when Kendrick lunged at him and he shot Kendrick, giving all of us enough time to get underneath our desks, to get ourselves safe and to run across the room to escape,” Giasolli said, adding that three other students also ran toward the gunman to apprehend him.

The student’s dad, John Castillo, told ABC News his son was a hero.

“I want people to know about him,” John Castillo said.