The 21-year-old was arrested by chance two weeks before April 20, exactly 20 years after two high schoolers killed 12 classmates and a teacher in the small Colorado town.
Police arrested the suspect after a neighbour alerted them over a drunken brawl at his home during which he was waving a machete at a homeless man.
Police found fake firearms as well as explosives and cans of petrol that the suspect allegedly planned to use to set fire to the school library, Dagens Nyheter reported.
The young man, who faces a hefty prison term, admits that he planned an attack but denies having the intention to kill, his lawyer Jan Kryo said told the paper.
However, a diary entry states: “I have always had this desire to kill, I don't know why… I don't want to seem crazy, but I may be a reincarnation of Eric Harris” — one of the two Columbine killers.
Harris, who was 18, and his 17-year-old accomplice Dylan Klebold turned their weapons on themselves after the bloodbath, then the worst school shooting in US history.