Police say a 12-year-old Arizona boy shot and killed his mother with a handgun after an argument. Cochise County sheriff's spokeswoman Carol Capas says deputies were called to a home Friday near Douglas on the Mexican border. They found 34-year-old Sara Madrid shot multiple times. She died at a hospital. The boy was booked into the county juvenile detention center on a charge of first-degree murder. Capas says the boy was at home with his mother, stepfather and a sibling when an argument broke out. The parents left, and when they returned the boy opened fire on his mom. No one else was hurt. Capas says she does not know what the argument was about.