CHEYENNE (WNE)  — A 15-year-old boy who caused a disturbance at Cheyenne’s Triumph High School and made threats against other schools last week was arrested Thursday.

Charles Rees Karn is being charged as an adult for making terroristic threats, a felony that carries up to three years in prison and/or a $10,000 fine. It was not immediately clear why Karn was charged as an adult.

According to court documents:

On Tuesday, Nov. 12, Karn caused a disturbance at Triumph, where he was a student. He was on probation for a different incident, and is accused of having an “emotional outburst that resulted in him cutting off his ankle monitoring bracelet and leaving the school on foot,” according to the probable cause affidavit.

After he left the school, Karn allegedly called Triumph and said he was going to blow up South High and Johnson Junior High, and that he also had a gun. Police later found Karn at Johnson, where he was vandalizing cars.

When officers approached Karn, he allegedly admitted to making the threats and said he wanted to scare people. Karn admitted he didn’t actually have a gun and “wanted to kill people” with the bomb threat, but said he was joking.

Due to his threats, five schools were placed on a secure perimeter, which included South, Triumph, Johnson, Goins Elementary and Rossman Elementary. South and Johnson were also searched for a possible bomb.

Police officers swept the schools with K9s to check for any threats, but no credible threats were found.