Three teenage boys allegedly threatened to attack a high school with homemade explosives and an “improvised firearm,” Duchesne police said Friday.

Duchesne deputies arrested the three boys — a 15-year-old and two 14-year-olds — after the threats were reported and two schools were put on lockdown Thursday.

During interviews with detectives, one teenager said he was supposed to be the shooter and the other two boys were to be the bombers in an Duchesne High School attack, according to a release from Duchesne County Sheriff’s Office.

Two of the boys had one small knife each, the release stated. Deputies also found two hand-drawn diagrams: one that showed how to build an explosive device and one with plans for building a firearm.

The teenagers have been referred to 8th District Juvenile Court on a count each of threat of terrorism, according to the release.

The boys were arrested after students reported to Principal Stan Young a threat similar to the 1999 massacre at Columbine High School, the release states.

Young put the school on lockdown at 1:40 p.m. Thursday and reported the threat to police. Nearby Duchesne Elementary School was placed on lockdown as a precaution.

Duchesne County deputies took a teenage boy into custody at gunpoint from a classroom at the high school, the release states. The other two teen suspects were detained and arrested.

A Uintah County sheriff’s K-9 trained to detect explosives searched the school and found no firearms or explosives. Police searched the campus and didn’t find threats. The lockdown was lifted at 2:35 p.m.

During their interviews with detectives, the teens reportedly said they had been bullied in the past, according to the release, and “didn’t think this was a big deal.”