BILLINGS, Mont. -- Prosecutors say a Montana man turned every parent's nightmare into reality when he chased down a 4-year-old girl at night in a park, snatched her while a friend watched helplessly, then raped and left her for dead on an American Indian reservation.

The U.S. Attorney's Office wants 22-year-old John William Lieba II sent to prison for life when he is sentenced Wednesday before a federal judge.

A jury convicted him of kidnapping, aggravated sexual abuse of a child and assault resulting in serious injury in the February 2016 crime on the Fort Peck Indian reservation.

Defence attorneys say Lieba had stopped taking his anti-psychotic medication prior to the kidnapping and could not remember the events. They requested a 30-year prison sentence.