ARLEE, Mont. -

An Arlee teen pleaded guilty to charges for murdering his stepfather and stabbing two others.

The attack took place last November when prosecutors say 17-year-old Nathan Adam Butler planned the attack, and sat in his room with a knife. Court documents go on to say Butler killed 51-year-old John Fisher, left his mother with critical injuries and another man with serious injuries.

Butler originally pleaded not guilty to three felony charges -- deliberate homicide, attempted deliberate homicide and assault with a weapon. Wednesday in Lake County District Court he entered guilty pleas to all three counts.

A sentencing hearing is scheduled for September.