"Their is no (identification) as yet on the occupant of the suspect vehicle involved," Orange county assistant police chief Wayne Miller told reporters.
But authorities are investigating the shooting as a case of hate crime, according to reports.
It adds to a growing list of such incidents targeting the community of Sikh Americans, said to be around 500,000.
The worst of them happened exactly six months ago wen six Sikh men were gunned down by a white supremacist Wade Michael Page at a gurdwara in Oak Creek, Wisconsin.
The community has been demanding treatment of these incidents as hate crimes, and lawmakers agreed at a congressional hearing on the Oak Creek shootings.
The Sikh American Legal Defence and Education Fund and 'Sikh Coalition' called on the law enforcement officials and requested them to conduct a thorough probe.