A 12-year-old boy shot his parents Friday with a .22-caliber rifle in the family home, killing his mother and wounding his father, Montgomery County police said.

The shooting occurred shortly before 4 p.m. and the boy surrendered to police after keeping them at bay for about 30 minutes."We have not yet determined what set this off," police Sgt. Harry Geehreng said. "We have no idea at this time."

The mother was found dead on the kitchen floor, said Gehreng.