FERGUS FALLS (AP) — An inmate at the Stillwater state prison has been convicted of threatening law enforcement officers and witness tampering.

A district court jury in Fergus Falls found 26-year-old Ramsey Kettle guilty of threatening two Fergus Falls Police officers and an Otter Tail County deputy along with a witness in another case.

Prosecutors say Kettle wrote letters saying that after he was released from prison he would strap explosives to his body and set them off inside the police station. Kettle has at least five previous felony convictions.

Sentencing is scheduled for May 31.