The boy cannot be identified for legal reasons.

Local media said the boy and his 34-year-old mother argued at the family home in August. After the boy's mother left the home, her son retrieved a pistol from her bedroom, waited for her to return and then shot her eight times. The woman's boyfriend witnessed the shooting.

The victim's sister testified Friday that the victim did not want the boy to live with her and was often abusive, yelling at him and hitting him.

"He is a docile, sweet boy," she told the court. Under Arizona law, the boy will be released when he turns 18. Sentencing is set for Jan. 23. Any sentencing outcomes will involve treatment, according to the boy's attorney, Sanford Edleman.

Edleman told AFP the crime was part of a tragic cycle which had seen the child's mother abused as a child.