An 11-year-old Arizona boy fatally shot his grandmother before turning the gun on himself after he refused to clean his room, according to the Maricopa County Sheriff's Office.

Doyle Herbert told police that he and his wife Yvonne Woodard, 65, who had full custody of the child, had repeatedly asked him to pick up after himself and clean his room on Saturday.

That evening the couple was watching television in their living room when their grandson, whose name has not been released, came up from behind Woodard and shot her in the back of the head, police said in a statement.

Herbert ran after his grandson but quickly returned to Woodard to give her aid, according to police.

As Herbert was tending to his wife, he heard another shot and saw the 11-year-old take a few steps before collapsing of a self-inflicted gunshot wound.

Police said the weapon belonged to Herbert and there were no prior signs that the boy might harm himself or someone else.

The Maricopa County Sheriff's Office said an investigation is ongoing.