An official close to the investigation says the fire at the Santa Monica house where a gunman began his killing rampage last week was intentionally set.
The official, who requested anonymity because the information had not yet been publicly released, said Wednesday that fires were started in a front living room and atop one of two twin beds in a room of the house.
Several boxes of matches were also found in the bedroom.
Firefighters found the bodies of the gunman's father and brother in a bedroom that was uninvolved in the blaze. The coroner's office says the father of John Zawahri died of multiple gunshots and his brother died from a shot to the chest.
Zawahri killed three more people before police killed him in the Santa Monica College library.