A man shot and killed his grandson Wednesday morning after the teenager began stabbing him and his wife, authorities said.

William Andrew Nation, 18, came to his sleeping grandparents' bedroom in their home about 20 miles south of Ava. He shouted that he couldn't take it anymore and then started stabbing them with a kitchen knife, said Chief Deputy Trampus Taylor of the Douglas County Sheriff's Office.

Jerry Garrison, took a handgun he kept by the side of his bed and shot his grandson several times, killing him, authorities said.

Garrison was stabbed in the head, shoulder and back, and his wife, Katie, was stabbed in the face. Jerry Garrison was treated at a hospital and released, while his wife was in fair condition Wednesday afternoon, a hospital spokeswoman said.

Taylor said a review could take several weeks, but it appeared that the shooting would be ruled justifiable.

The teen had lived with his grandparents about a year. They said he had been hearing voices and had seen a psychiatrist on Monday, Taylor said. He was scheduled to return to the psychiatrist in a couple weeks.

An Ava phone number listed under Jerry Garrison's name was not in service.