STILLWATER, Minn. (AP) - An inmate at a Minnesota maximum security prison is accused of strangling a fellow prisoner with a shoelace last December.

Washington County prosecutors have charged 40-year-old Benjamin Beck with second-degree murder in the death of 30-year-old Shane Cooper.

Cooper and Beck were inmates at the Oak Park Heights prison when Cooper was found strangled in his cell.

According to the complaint, investigators found Beck's identification card in Cooper's room and used surveillance footage to verify Beck had entered the room before Cooper was killed.

Beck told investigators he had been Cooper's "protector" at prison. But the complaint says when Beck discovered that Cooper was a convicted child rapist, he didn't have "a way out" and killed him.

Beck does not have an attorney yet.