Transcript for Deadly school shooting in Colorado revives painful memories for community
Everyone's freaking out. My heart is racing, because it felt like it was coming out of my chest. Reporter: It's the text message every parent dreads. Dad, the school is on a lockdown. Reporter: Trapped inside a school with an active shooter on the loose, begging for help. Dad, there's gunshots. Oh, my god. Reporter: You're reading these text messages, what's going through your mind? Anything that would go through any parent's mind. I'm scared, getting nervous. I have never been in a situation like this. I was scared out of my mind. Everyone else was scared out of their mind. It was painful to look around and see how scared they were. I can't comprehend that this even happened. Reporter: It's now a depressingly familiar story of loss, the lingering trauma and heroism demanded of our nation's youth. I happened to be on the right side and able to get the gun away from him. Reporter: A community forced to join others in a school shooting, this time at the stem school highland's ranch. Nine students shot, one fatally. It was senior Kendrick Castillo who sacrificed everything. Ken lunged at him. He shot Kendrick, kifing all of us enough time to get underneath our desks to get safe and run across the room to escape. He did what he had to do. I knew that was my son's nature. That was who he was. He was going to protect people. Reporter: His parents telling us they weren't surprise the by their son's courage. An aspiring engineer, only days away from graduation, Kendrick loved to tinker. We'd build robots together. We worked on cars together. That was our life. I loved that. I want to make something very, very clear. Kendrick Castillo khaied died a legend. He was a foot away from the shooter. Instead of running the opposite direction he ran towards it. Reporter: 18-year-old recruit helped fight off the attacker. I'm not a victim. I refuse to be a victim. Kendrick refused to be a victim. The other students refused to be a victim, and I will live the rest of my life, whether it be this situation, a situation, in any other situation I encounter, I'm not going to let somebody get the upper hand on me. Reporter: It was just after lunch at the stem school when students were thrown into a panic. Getting information on a shooting. Reporter: Two students arm the with handguns started firing deep inside the school. A shooter in room 107. Some of us hid behind the weight machine and some in the corner. That's where me and my two friends were hiding, in the corner. It was terrifying. Reporter: Police rushed to the scene. We're trying to get a suspect. We have one person shot in the lower back. School's in lockdown. Reporter: The arrived minutes later, with bullets flying. Shots fired. The first officers that arrived at the scene had to force their way into the school. Reporter: Immediately, officers come face-to-face with one of the shooters. There's more gunshots coming from the office. Reporter: Students in class had managed to restrain the You have the shooters? In classroom 105. They took that person into custody and then started to search for the other person. Reporter: But with one assailant still at large, police scrambled to clear the school of threats. According to the first shooter, the second shooter's still on the loose. Reporter: Meanwhile, more than 1 students desperately try to escape the shot the. When we were walking out, I don't know if it was a dead body or something to my right with bullet shells, and a cracked then when we were entering the building there was a trail of blood. Reporter: Some fleeing to neighbors' yards. We got him up, got him into my back yard, and slowly we got him up my steps into the kitchen. Reporter: Finally, the second assailant is apprehended on the opposite side of the school. Stay right here on the east side of the school. We got two in custody now. More buses coming in! Reporter: With the two shooters in custody, students were bussed off campus as parents frantically searched for their children. I just want to get to my son and hold him. He's terrified. The last two hours have been the worst two hours of my life. Reporter: And less than two hours later, those reunions and the tearful embraces. Dylan! Love you, son. Reporter: Today, a suspect appearing in court, 18-year-old Devon Ericson, that stripe of fuchsia in his hair, nails painted black, saying a single word in his first appearance. No. Reporter: Nodding vigorously, when the judge addressed him, never looking up. He and a 16-year-old accomplice facing nearly 30 charges, including murder. This attack adding to the growing list of shootings across the nation from parkland, Florida to Santa fe, New Mexico and yet another in the Denver area. There's been a day of horror in Littleton, Colorado. A terrifying moment in Littleton, Colorado. A night at the movies has turned into a nightmare. Reporter: This attack seven miles away from columbine high school where 20 years ago two gunmen opened fire, killing 13 and wounding many others. If you had suggested to anyone behind my or in this room that within 20 years and 20 miles we would have dealt with columbine, the Aurora theater, arapahoe high school, the shooting of Zack parish and other deputies we would have thought you mad, yet here we are again. Reporter: At the time the police policy was to wait outside for the S.W.A.T. Team to arrive. A 45-minute delay that was criticized for allowing the gunman to continue their killing spree. Lessons learned that shaped how officers and students approached this most recent shooting. We had officers on the street that were there with inside two minutes. Once at the school they immediately engaged the suspects. And started to rescue the children that were injured. Reporter: A reaction Colorado officials have long been training for, heading drills in the same county and in schools just miles away from where this shooting happened. There's got to be an immediacy, an aggressive action. We need to go in and stop the Reporter: But officers are no longer the only ones being prepared for mass shootings. Active shooting drills are now part of many schools' curriculums. When the shooting began at the stem school, 12 year old Nate Holley told CNN he was hiding but ready. I had my hand on a metal baseball bat just in case. Because I was going to go down fighting if I was going to go down. Reporter: And just last week, 21 year old Riley Howell lost his life after charging a shooter, he, too, remembered as a hero. At his funeral this week Howell buried with military honors. Thank you for being the brother I never had. Thank you for being my hero before everyone's. Reporter: Students like Chris Elledge are dealing with a new reality. I'm trying to take deep breaths. Reporter: Is it because you still see yourself in that moment? You feel that? I can't. I can't. Reporter: Can't what? There's no possible way to put myself in that position Reporter: As this Denver community comes together to honor the life of its hero. If I could trade places with him, I would do it. Reporter: And Kendrick's family faces a future without its child. People say what can I do? How can I help you? You know what? If you have kids, hug them. Teach them to be good kids and pray. Our thanks to Matt Gutman for that report. And tonight our hearts are with the community of highlands ranch.
This transcript has been automatically generated and may not be 100% accurate.