A 34-year-old Oklahoma City man has been indicted by a federal grand jury, after investigators say he made online threats against the city of Casper.

According to the FBI, on January 14th, Glenn Kirkham posted a threat on a popular online forum “4chan,” claiming Casper-area residents might be in danger. He claimed he would launch an attack using baseball bats, knives and firearms.

The Casper Police Department received numerous calls from across the country regarding the threat, and area schools were placed on lockdown while the investigation was ongoing. He was arrested a short time later in Oklahoma City. Prosecutors say they don’t know why he targeted Casper in his post.

The federal indictment accuses Kirkham of transmitting a threat by interstate communications. A conviction could carry a five-year federal prison sentence, along with fines of up to $250,000 and restitution to law enforcement agencies for the cost of the response to the incident.