SIOUX FALLS, S.D. (AP) — A South Dakota man accused of stabbing a man in the back of the head has been sentenced to a year in prison.

Twenty-year-old River Grey Bull, of McLaughlin, pleaded guilty in May to a federal charge of assault with a dangerous weapon. The incident happened Jan. 24 on the Standing Rock Indian Reservation.

Authorities say officers could not initially find Grey Bull when they arrived at the scene, but later spotted him near a patrol vehicle. He allegedly had blood spots on his sweatpants.

Grey Bull was also ordered to serve three years of supervised release.

A federal public defender could not be immediately reached for comment.

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