Arizona grandmother Yvonne Woodward asked boy, 11, to clean his room. He shot her dead, then killed himself

An Arizona boy fatally shot his grandmother and then killed himself on Saturday after being instructed to clean his room, his grandfather told authorities.

Doyle Herbert called police at about 5pm to report his wife and their 11-year-old grandson were dead in an apparent murder-suicide, a spokesman for the Maricopa County Sheriff’s Office, Joaquin Enriquez, said in a statement. Hebert told authorities the boy shot his 65-year-old grandmother, Yvonne Woodward, in the back of the head after they’d asked him repeatedly throughout the day to pick up after himself.

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The boy was apparently “being stubborn about it”, according to the statement. After killing his grandmother, the boy turned the handgun – which belonged to his grandfather – on himself, the statement said.

The couple had just sat down in their living room in their Litchfield Park, Arizona, home, located about 30km west of Phoenix, to watch television when the boy approached his grandmother from behind and shot her, the statement said.

Herbert told police he initially chased after his grandson but stopped to perform first aid on his wife. Moments later, he heard another gunshot, saw his grandson take a few steps, then collapse to the ground. Herbert retrieved the weapon and called 911, police said.

Neighbours told a CNN affiliate that the boy was known for playing around the neighbourhood and was part of a “nice family”.

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“It really hasn’t set in just yet. I mean this is a nice neighbourhood, it’s really quiet – as you can see – it’s just a tragic, tragic thing,” neighbour Walter Venerable told news website azfamily.

The boy’s grandfather told detectives he and his wife had full custody of their grandson. Investigators have not found evidence that suggests the boy wanted to harm others or himself before this incident.