HELENA, Mont. (AP) — A Montana man who had reportedly threatened to commit a Columbine-style attack at a high school has pleaded guilty to federal charges of illegally possessing homemade bombs and a silencer.

Logan Sea Pallister, 25, of Helena entered his pleas Tuesday in U.S. District Court in Great Falls. He faces up to 10 years in prison when he is sentenced on May 22, the Independent Record reported.

The case began in May 2022 when a witness told Helena Police that Pallister had multiple bombs, access to multiple firearms and had been making threats to attack Helena High School, court records said. Pallister was arrested a week after an 18-year-old gunman entered a school in Uvalde, Texas, killing 19 children and two teachers.

Pallister had multiple homemade bombs, and there were several firearms and ammunition in his car, court records said.

Other news 1st major storm of the season drops up to a foot of snow in Montana

Federal prosecutors said Pallister intended to “maliciously damage” public school buildings and took a “substantial step” toward that goal before his arrest. Court documents did not provide further details on the alleged plans.

Pallister had posted photos on social media of him holding weapons and wearing a trench coat, as the shooters at Columbine High School in Colorado had done in 1999. Twelve students and a teacher died in the Columbine shooting. The two shooters killed themselves.

The witness went to police after Pallister reportedly showed him a small propane canister with a fuse sticking out of one end and despite threats that Pallister would kill the witness if they told authorities, court records said.

“We are grateful to the individual who bravely alerted law enforcement to Mr. Pallister, and to our Helena Police Department whose response led to his apprehension and arrest,” Helena Public Schools Superintendent Rex Weltz said.

Pallister also faces an April trial on related state charges, Lewis and Clark County Attorney Kevin Downs told the Independent Record.