The senior class of the Highlands Ranch STEM school were only three days from graduation when two gunmen entered the school and opened fire. While terrified students sought cover, however, Kendrick Castillo charged forward, ultimately sacrificing his own life to subdue the assailant.

ABC News reports, the 18-year-old reacted to the shooting immediately and was able to pin the attacker to the wall before he was fatally shot. Castillo’s bravery inspired two other students to come forward as well and together they were able to disarm and subdue the gunman before any more were killed.

One of the two who ran to assist Castillo was Brendan Bialy, a U.S. Marine recruit. Bialy, who walked away unscathed described Castillo as an unstoppable bowling ball:

“Basically when he gets moving there’s no stopping him,” Bialy told Fox News, before adding, “I love that kid. He died a trooper. He got his ticket to Valhalla, and I know he will be with me for the rest of my life.”

Wednesday morning, John Castillo, Kendrick’s father, told the Denver Post:

“It doesn’t surprise me. He cared enough about people that he would do something like that, even though it’s against my better judgment.” “I wish he had gone and hid,” Castillo continued, “but that’s not his character. His character is about protecting people, helping people.” “He was the best kid in the world,” his father added through tears.

By all accounts Kendrick had a bright future ahead of him. He was a lover of robotics, fishing, hunting, and automobiles. His close friend and fellow senior, Nui Giasolli, said their fathers are both Knights of Columbus and Kendrick would always tag along with his father to volunteer his time to the organization. After high school was over, it was Kendrick’s intention to join the Knights as a formal member.

Cece Bedard, who knew Castillo since elementary school, said he was especially good at connecting with the elderly. She said:

“There is no doubt in my mind that he would have done anything he thought he could have to help anyone.”

His friends remember Kendrick as a goofy jokester, but his humor was never at anyone’s expense. Bedard described him as a boy with a strong sense of self, who was not swayed by peer pressure or others’ opinions of him. He was also a member of STEM’s regional robotics team.

The attacker Kendrick helped subdue was accompanied by a second shooter, who was apprehended by a security guard. District Attorney George Brauchler said he has not decided whether both shooters should be tried as adults, but both are old enough to be treated as such.

The shooting happened just two weeks after the neighboring town of Littleton marked the anniversary of the Columbine shooting, which claimed the lives of 13 people. The two schools were separated by about 7 miles in the city of Denver.

On Thursday morning Archbishop Samuel J. Aquila made a Facebook post in which he praised the actions of Kendrick and said he would offer a Mass in Castillo’s name: