Kendrick Castillo, the hero of the Colorado shooting on Tuesday, was graduating this week from High School

HIGHLANDS RANCH, Colo. – He was a high school senior, set to graduate this week.

But instead of celebrating Kendrick Castillo’s graduation, the family of the 18-year-old will be mourning his death.

Castillo, a senior at STEM School Highlands Ranch in suburban Denver, was killed in a classroom Tuesday in a shooting that police say was carried out by a pair of his classmates: 18-year-old Devon Erickson and a younger classmate who has not been identified because she is a juvenile. Eight other students were wounded.

The shooting happened at the end of the school year during a British literature class. The toll exacted by the shooters could easily have been worse. Deputies arrived within two minutes of the first call, officials said. A security guard restrained a shooter. And accounts provided by students and by a military official suggest that Castillo and several classmates sprang into action when the shooters began firing.

It was a moment that encapsulated some of the accumulated horrors of the past 20 years: School shootings, once unthinkable, have become common enough that some students now fight back.

It also marked the second time in a week that targets of a shooting at a school appeared to play a role in quelling it: One of the students killed in a shooting last week at the University of North Carolina at Charlotte has been hailed for his role in thwarting the attacker there.

Nui Giasolli was in class in Colorado, expecting to have a fun end-of-year session analyzing comedic effect in the 1987 film “The Princess Bride,” when an 18-year-old classmate walked in late, which he often did. She said she didn’t think much of it, until he shut the door, pulled out a gun and told the class, “Don’t anybody move.”

Giasolli froze and went blank. Then she thought it must be a joke. She heard her teacher say something like, “Gun. Get down.”

Then the classmate started shooting, and Giasolli saw Castillo and several others lunge to try to get the gun. She ducked under a desk. She didn’t see any hesitation from Castillo, she said. If he had any hesitation, she said, “he threw it out the window.”

The classmate shot Castillo, and that gave others time to hide under desks or run, she said. As the shooter ran, several boys in her class tackled him.

Written by Abelina Tavera