The Associated Press says the gunman took his own life as a sheriff's deputy got close.
'This is highly unusual to have six people shot and dead in one incident, ' Kern County Sheriff Donny Youngblood told The Bakersfield Californian.
The attacker then fatally shot two more men at another location, before hijacking a auto with a woman and a child on board. Sheriff's deputies say a husband and wife went to a business, and the husband shot and killed his wife, as well as a man inside the business.
Officials provided no immediate details Thursday morning on what prompted the shootings Wednesday evening at a home and a trucking company in Bakersfield, about 90 miles (145 kilometers) north of Los Angeles.
When another man showed up, the gunman began to give chase.More news: Trump dismisses Woodward book as 'joke'
"Obviously, these are not random shootings", the sheriff said.
Sheriff Youngblood later told reporters his team was carrying out an investigation into the mass shooting. He drove to a nearby highway where he pulled over into a parking lot when he saw a deputy.
One man was shot outside a sports store near a trucking company where the gunman killed two others.
Investigators said he next stole a vehicle with a woman and child inside, but they were not harmed.
The identity of the suspect and victims has yet to be released.
At least five crime scenes were being investigated as deputies worked to backtrack the shooter's footsteps. A third man who arrived at the business was also pursued and shot.