When Sara Haynes heard about the shooting at STEM High School in Highlands Ranch, Colorado on Tuesday, she prayed. A Catholic school teacher in Denver until just recently, she knew some of her former students were now high schoolers at STEM.

When Haynes learned that Kendrick Castillo, a former student of hers, was the lone casualty in the May 7 shooting, she cried immediately.

Then she reached out to the other students who had been in the same 7th and 8th grade math and religion classes at Notre Dame Catholic School as Castillo. Details of Kendrick’s death were not yet public, but her students guessed Castillo had died trying to protect others, Haynes said.

“I went to my students and we were all just sharing together. And I said: ‘Do you guys think that he blocked the shooter?’ And they said: ‘Yeah.’ I mean, it just wasn't a shock to us” that he would give his life for others, Haynes said.

On Wednesday, Kendrick’s father, John Castillo, confirmed to the Denver Post what he had learned from witnesses and the coroner: that Kendrick died while charging the shooter to save his friends.

“It doesn’t surprise me,” John Castillo told the Denver Post. “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 added, “but that’s not his character. His character is about protecting people, helping people.”

Kendrick’s friends and fellow students share the same sentiment, Haynes said.

“Every time I see a new kid that is in shock or crying, I ask - ‘But are you surprised?’ And they say ‘No, I’m not surprised at all. I’m just mad because I didn’t want him to have to do it. But of course he was going to do it.’”

Haynes said she remembers Kendrick as an unfailingly kind student, who cared deeply about everyone, who tried hard in school, and who wasn’t afraid to have fun and be goofy.

“Kendrick is probably one of the funniest people I've ever known,” Haynes said. “He's really quirky and sweet. And quiet, but not really. He's one of those kids that he knows the appropriate time to be quiet, and then when it's the appropriate time for him to just be a total dweeb, he'll be a total dweeb.”

He was always joyful, Haynes said, and funny - as her trove of goofy videos of Kendrick prove, she said. The only time when he was not joyful was at parent-teacher conferences, Haynes recalled. Kendrick tried hard in school, and he loved technology and excelled at science - but math was harder for him, she said.

“He would get so serious at parent-teacher conferences because he struggled academically and...most middle school kids put blame on other people, but he just always took the responsibility so seriously that he would cry,” she recalled.

“And we would tell him, ‘You don't need to cry! We just want you to turn in your work.’ And he'd be like, ‘I'm so sorry.’ He really was such a deep thinker even if he didn't look like it, because he was so jolly. He had this joy that shone through.”

Sr. Loretta Gerk was another teacher who knew Kendrick while he was a student at Notre Dame Catholic School - she taught him in physical education classes, from Kindergarten through eighth grade.

“He was the neatest kid,” Gerk told CNA. “He was so kind and gentle, but yet, he was all boy too, you know what I mean?”

Gerk said that she would sometimes worry about the kind and gentle students, because they could be prone to teasing. But no one ever teased or made fun of Kendrick - he was just too likeable, she said.

“Kids are sometimes cruel to each other,” she said. “But the kids weren’t mean to him. You couldn’t be mean to him.”

“If any little kids were crying or something, he would go talk to them. He would reach out to them. He would notice those things,” Gerk said.

Gerk said when she found out Kendrick had died in the shooting, her heart and her stomach hurt. When she found out he had died trying to rush the shooter, she thought: “That doesn’t surprise me at all.”

A hunter who loved his elk hunting trips with his father, Kendrick’s familiarity with gun safety may have given him additional courage when he rushed the shooter, Gerk said.

Not only was Kendrick kind in school, but he was also a very helpful and active person at church, Gerk recalled. He would often tag along with his dad to Knights of Columbus events, Gerk said. He would usher at Mass with his dad on Saturday nights, and help serve breakfast with the Knights of Columbus during Catholic Schools week.

“Kendrick would be in the kitchen, and he had a blue apron that said ‘Knights of Columbus.’ Kendrick was in there with his dad, helping,” she said.

Cece Bedard knew Kendrick because her dad, too, was in the Knights of Columbus. In a message to CNA, Bedard said that Kendrick “loved his faith and he really loved to serve others.”

It was not just that Kendrick did one heroic act, Bedard said, but “he lived the life of a hero, always helping others to the point where I’m not quite sure what he did for himself.”

He loved his Catholic faith, Bedard said, and once told her when they were young that although he couldn’t picture himself being a priest, he thought “the way of life (of a priest) was simply beautiful.”

“He truly was a living saint,” Bedard said.

Deacon Chuck Parker knew Kendrick at Notre Dame parish, where he remembers him as an altar server and a young usher, and a favorite greeter at the doors of the church.

“If anybody could exemplify a minister of hospitality it was Kendrick,” Parker said. “Even at such a young age, he was always very kind and compassionate, very engaging with people…people loved coming in and being greeted by Kendrick.”

“You hear a lot of people say that he was really a good kid,” Parker said. “And he was really a good kid, he just really was.”

Parker, like many others, said he “wasn’t surprised” when he heard how Kendrick died, “because he was such a loving kid.”

“I was thinking about John’s Gospel where it says that there’s no greater love than to lay down one’s life for one’s friends. And that was Kendrick,” he said.

In religion class, Haynes said Kendrick was pensive, hungry for the faith, and always eager to play Jesus whenever they acted out stories from the Bible.

“He always wanted to be Jesus,” Haynes said. In a video from her class that she posted to Facebook, Kendrick acts out the part of Jesus, going to search for his apostles or to comfort a suffering person, blessing them with the sign of the cross and inviting them to join him.

“I have this amazing scene where he found the two apostles and they're all kneeling in front of the camera...Kendrick is peering at the camera and then he does the sign of the cross at everyone watching. And he was so serious in it,” Haynes said.

While religion can sometimes be a difficult subject to teach junior high kids, Haynes said that whole class “was really on a spiritual journey that I just got to witness. They really wanted the faith. And they weren't afraid to ask the tough questions and to be stuck with some of the answers.”

Haynes credits Kendrick’s parents for raising him to be a kind and faithful young man, and she urged everyone to continue to pray for them for the rest of their lives.

Now a parent herself, Hayes said that while she hopes she never has to experience the tragedy of losing a child, she wants her two boys to grow up to be “just like Kendrick.”

Because of her faith and because of how he died, Haynes said she believes Kendrick “went straight to heaven.”

“I don't think there's any doubt.”