Teen Arrested Alleged Columbine-Style Plot

Oregon police say they have thwarted a plan to blow up a high school.
3:52 | 05/27/13

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Transcript for Teen Arrested Alleged Columbine-Style Plot
Arlington cemetery, a clear reminder of why we celebrate this day. A fast-moving developments in oregon. Police say they have stopped a frightening plot to blow up a high school. The suspect, planning to cause more death than columbine. He's now in custody. And abc's linzie janis is here with overnight developments for us. Reporter: Prosecutors say 17-year-old grant acord, seen in this facebook photo, was on a mission to blow up his oregon high school. This morning, he's being held at a juvenile jail, after police say they found a deadly arsenal, including homemade bombs, hidden under the floor boards of his bedroom. Police say they. Reporter: Tipped off late thursday by a 911 caller, who said acord was pnning an attack and wanted friends to film it. They briefly searched his mother's house that night and returned with the bomb squad friday. Inside, they say they found pipe bombs, bombs made from drain cleaner, homemade napalm and molotov cocktails. This individual manufactured devices that would have been capable of causing injury or death. Reporter: Prosecutors do not have a motive for the attack. But found detailed plans in journals. Even a timeline. Checklists, diagrams, inspirations. Sources. And a focus on re-ting the model of columbine. Reporter: Fellow students describe acord as shy and aloof. I say to hi to him in the hallway. I was like, well, I should probably talk to this kid. Maybe sure he feels okay. Reporter: This morning, the school superintendent said police and bomb dogs have swept the high school twice and found nothing inside. The 17-year-old is due in court on tuesday, where he will be charged as an adult. And overnight, a shocking revelation. One student telling reporters, he remembers acord striking up a conversation randomly at school, about making bombs. A red flag. They swept the school? They swept the school. It's clean. I want to bring in brad garrity, a former fbi special agent. Brad, good morning. Good morning, david. It's stunning to hear when these point back to columbine so many years ago. Police say he wanted to outdo them. Why does that attack so resonate with these troubled teens? That's because that was the first major attack by two students. And was, up until cho at virginia tech, the most lethal. And even cho referred to klebold and harris. What is interesting, is klebold and harris referred to timothy McVEIGH AT OKLAHOMA CITY, EACH Trying to outdo the other. You heard the young man there in linzie's report, saying i talked to him because he seemed like a loner. And the other heard a red flag raised and mentioned this. What do you look for? And what should you do? Every one of these school shootings or bombings are premeditated. The kids tend to talk to other kids, via the net or in person. So, there's a lot of inftion out among the students about someo is about to commit an act like this one. So, the key is, communication between school management and the students is critical, so they feel okay to step forward. In this case, I believe one of them called the police. As you know in so many of these cases, these are lone wolves that blend right in. Tips for all of us. What do we do to spot them? They are loners. They will mention things. They'll have inappropriate behavior. They're probably depressed. And they almost exclusively are isolated. Brad garrett, joining us from washington. It was a crash-filled race

This transcript has been automatically generated and may not be 100% accurate.

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