(ALBANY, Ore.) -- An Oregon high school student accused of plotting to blow up his school had approached classmates to talk about bombs weeks before his arrest, according to students.
Grant Acord, 17, a junior at West Albany High School, was arrested late Thursday at his home on two counts of possession of a destructive device and two counts of manufacture of a destructive device, according to the Albany Police Department.
But prosecutors say he will be charged as an adult with aggravated murder and is expected to be arraigned Tuesday in Benton County Circuit Court.
West Albany High School student Thomas Stone said Acord approached him in class two weeks ago and initiated a conversation about bomb-making materials.
"He was just, just kind of randomly came up to us and started talking about the different materials that you need to make a bomb," Stone told ABC News affiliate KATU-TV. "Like, he was describing how to make one, which thinking back should have brought up more suspicion."
"You know, I didn't think much of it 'cause he's kind of a strange kid," Stone added. "So I wasn't surprised he had some strange hobbies, you know?"
Keagan Boggs, another West Albany student, said he overheard Acord approach a group of students and mention bombs.
"It wasn't like 'Oh, I'm making bombs, I'm gonna blow stuff up,'" Boggs told KATU. "It was just talking about it, like something that you wouldn't really think like 'Oh, he's gonna blow something up. Like a school.'"
Benton County District Attorney John Haroldson said the teen had a detailed plan, timeline and a deadly cache of weapons "specifically modeled after the Columbine shootings," that killed 13 people and injured 21 more in 1999.
According to Haroldson, the explosives police allegedly found hidden in a secret compartment under the floor of his bedroom included pipe bombs, Molotov cocktails, napalm bombs and explosives made from drain cleaner.
Acord had also picked a date for the plot to unfold, according to Haroldson, but he would not elaborate.
Police were alerted to the case by a tip from a 911 caller that Acord had made a bomb, planned to blow up his high school and asked friends to film the incident when it happened, officials said.
Other classmates at West Albany High School described Acord as a "happy" and "nice" person.
"I'd say 'hi' to him in the hallway, cause I was kind of ... was like, 'Well, I should probably talk to this kid ... make sure he feels OK,'" West Albany student Dennis Reilly said. "So, I'd talk to him sometimes and he seems like a pretty nice guy."
As Acord heads to court Tuesday morning, his classmates will be heading back to school after the Memorial Day weekend, thankful the alleged plot was foiled.
"I was just, like, shocked and like even more thankful we are all still alive," said Boggs. "Because he could have, he had plans, like he could have done it any day. He obviously was ready. He was just waiting for the right moment."
The school's superintendent said police and bomb dogs have swept the high school twice and found no devices.
Copyright 2013 ABC News Radio