A 12-year-old boy who fatally shot his mother after an argument over his chores was found guilty of premeditated murder.

Judge James Conlogue found the boy guilty after a hearing Friday in Cochise County Superior Court in the southern Arizona town of Bisbee. The boy is not being identified because he was charged as a juvenile.

Conlogue ruled that prosecutors had proved the boy acted intentionally and with premeditation when he shot Sara Madrid, 34, eight times on Aug. 1. The shooting happened after the boy had argued with his mother over his chores.

Madrid had left the family home after the argument, and the boy got a .22-caliber pistol from her bedroom closet, waited for her to return and then repeatedly shot her, according to court testimony.

Madrid's live-in boyfriend of 10 years, Alfonso Munoz, witnessed the shooting and said the boy gave him the empty gun afterward.

Munoz, who helped raise the boy, said he had taught the child how to use the weapon for emergencies and self-defense.

The boy's lawyer, Sanford Edleman, had argued that the boy did not intend to kill his mother but only wanted to get back at her for abusing him.