Authorities say Dorner may be driving a 2005 charcoal gray Nissan Titan pickup truck. They believe he changed his license plate from 7X03191 to 8D83987.
The suspect is considered armed and extremely dangerous. A blue alert has been activated in the following counties: Kern, Santa Barbara, Ventura, Los Angeles, San Bernardino, Orange, Riverside, San Diego, and Imperial.
Dorner, 33, is described as an African-American man standing 6 feet tall, weighing 270 pounds. He has black hair and brown eyes. If seen, call 911.