MISSOULA, Mont. (AP) — A registered violent offender has pleaded guilty to a federal charge of transporting a minor with the intent to engage in criminal sexual activity.

Federal prosecutors say 60-year-old Rodney Lee Zahn entered his plea on U.S. District Court in Missoula on Jan. 17. He faces a mandatory minimum of 10 years in prison when he is sentenced on May 18.

Prosecutors say Zahn befriended a developmentally delayed 16-year-old girl and her family and left Sheridan with the girl early on Aug. 3. They were located the next day in Cheyenne, Wyoming and Zahn was arrested.

Prosecutors say Zahn admitted he had sexual intercourse with the girl twice and that he knew she was 16.