The attack at Half Moon Bay comes only two days after a mass shooting in Monterey Park.
Image source, CBSA gunman killed seven people before being arrested in California on Monday, just two days after a shooting claimed 11 lives at a popular dance hall.
The latest attacks occurred at two separate locations in the coastal city of Half Moon Bay, about 30 miles (50 km) south of San Francisco.
The attacker was identified as 67-year-old Zhao Chunli, a local resident.
It comes as the state mourns the deaths in majority-Asian Monterey Park during celebrations for the Lunar New Year.
The suspect on Monday was filmed by news cameras turning himself in to the San Mateo County Sheriff’s Office about two hours after the attack.
The first four victims were discovered at a mushroom farm around 14:22 local time (00:22GMT), while the other three were later found at a nearby trucking business.
Investigators have not yet provided a motive for this attack.
San Mateo County Sheriff Christina Corpus said at a news conference that the suspect was arrested after driving himself to a local police station around 16:40.
He was found with a semi-automatic pistol that may have been used in the attack, and is currently “co-operating” with police, she added.
Mrs Corpus added that an eighth victim is being treated in hospital and is in critical condition.
“This kind of shooting is horrific,” she said. “It’s a tragedy we hear about far too often, but today it’s hit home here in San Mateo County.”
In a news conference, the sheriff also confirmed that witnesses include children who had recently been let out of school and lived on the rural property.
“For children to witness this is unspeakable,” she said.
Image source, Police handout/ CBS
California Governor Gavin Newsom tweeted that he was “at the hospital meeting with victims of a mass shooting when I get pulled away to be briefed about another shooting.
“This time in Half Moon Bay. Tragedy upon tragedy.”
Half Moon Bay Council member Debbie Ruddock told NBC that the victims were Chinese farmworkers.
San Mateo County Board of Supervisors President Dave Pine told the Associated Press news agency that the attacks were committed by a “disgruntled worker”.
“We are sickened by today’s tragedy in Half Moon Bay,” Mr Pine said in a statement.
“The scourge of gun violence has sadly hit home. We have not even had time to grieve for those lost in the terrible shooting in Monterey Park. Gun violence must stop.”