An 11-year-old boy in Arizona fatally shot his grandmother in the back of the head Saturday evening and then turned the gun on himself after she asked the boy to clean his room, police said.

Doyle Hebert, who along with his wife Yvonne Woodard, 65, had custody of their 11-year-old grandson. Herbert told authorities that his grandson fired a bullet into the back of his grandmother's head, FOX 10 reported. Herbert was sitting on the couch at the time, the report said.

Hebert told police that he first chased after his grandson, but heard another gunshot when he went back to tend to his wife, The Arizona Republic reported. The boy had turned the gun on himself.

The weapon reportedly belonged to the grandfather.

Authorities are investigating the incident that occurred at a home in Litchfield Park, AZ., which is about 21 miles west of the state’s capital. Police said they have found nothing that would indicate the boy wanted to commit acts of violence prior to the shooting, the station reported.