Authorities in Albany reacted quickly to the tip and seized homemade bombs hidden in the bedroom of Grant Alan Acord, a student at West Albany High School.
Acord was arrested Thursday and is being charged as an adult.
The Albany Democrat-Herald reported that he will be arraigned Tuesday in Benton County Circuit Court on one count of aggravated attempted murder and six counts each of manufacturing a destructive device, possession of a destructive device and possession of a weapon with intent to use it against another person.
Investigators found the bombs under floorboards of Acord's bedroom at his mother's home. Haroldson said Saturday at a news conference.
Investigators seized a plan, checklists and a diagram of West Albany High School. Among the documents was a date in which the youth planned to set off the bombs and firearms in an incident that was "specifically modeled after Columbine," Haroldson said.
Two students in 1999 fired weapons at Columbine High School in Littleton, Colo., killing 13 and wounding 21.
"This is a case of a planned assault on a target-rich environment and that target-rich environment is the West Albany High School," Haroldson said.
The North Albany home of Acord's father also was searched and more explosives were found, Haroldson said.
A search of the school found no explosives.
No motive has been identified, Haroldson said.
Acord's plans, he said, revealed "inspirations and a focus of recreating a model of Columbine with some adjustments that would make it more successful."
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