Authorities found at least six crime scenes, an Orange County sheriff department spokesman said.
Tustin police supervisor Dave Kanoti said the shootings started with an apparent car-jacking yesterday morning. Police then received reports of shootings in several locations.
The alleged gunman shot himself on an intersection, Mr Kanoti said, adding that it was possible that more people had been shot, as some may have chased the gunman.
The condition of the wounded victims was unknown.