LEBANON, Mo. (AP) - Investigators say a southwest Missouri man shot and killed a man and injured a teenager because he was waiting for the man's wife to leave him.

Matthew Mitchell Rumbaugh, 65, of Mountain Grove pleaded not guilty Wednesday to first-degree murder, first-degree assault and two counts of armed criminal action.

He is being held in the Laclede County jail with no bond, charged with shooting of Chad Gerber in Grovespring at Gerber's home early Tuesday.

Gerber's 15-year-old son is hospitalized with a gunshot wound to the head.

A probable cause statement says Rumbaugh told an investigator he shot Gerber because he was tired of waiting for Jennifer Gerber to leave her husband.