13-year-old boy wounded by gunfire at Oakland, Calif., school

A 13-year-old boy is in stable condition and is receiving treatment after being shot outside a school in Oakland, Calif.

A 12-year-old boy, a schoolmate of the victim, is believed to be the shooter and is in custody. The gun he allegedly used has been recovered, KGO-TV reports.

The shooting occurred Monday at Madison Park Academy in Oakland, which serves students in grade six through 12.

Police said they do not know the motive of the shooting.