From a Moraga Police Department press release:
On Friday, 5/4/2012, a 13 year old student brought a 4″ device to Joaquin Moraga School and was discovered showing it to other students by school staff. The device was taken to an office and Moraga Police were called at 2:45 PM. Upon arrival, the device was inspected, the area secured, and the Walnut Creek Bomb Squad was called to respond.
The Bomb Squad verified the contents qualified it as an explosive device. The device was disassembled and removed from campus. Possession of the explosive device on school grounds is a felony and the student was deteained by MPD after searching the student’s residence for any additional devices with none found.
The 13 year-old was released to parents and the case will be referred to the Contra Costa County DA for disposition.