A gunman killed seven people before being arrested in California on Monday, just two days after a shooting at a popular dance hall left 11 dead.
The latest attacks occurred in two separate locations in the coastal town of Half Moon Bay, about 30 miles (50 km) south of San Francisco.
The attacker has been identified as 67-year-old Zhao Chunli, a local resident.
It comes as the state mourns the deaths in the predominantly Asian Monterey park during Lunar New Year celebrations.
On Monday, the suspect was filmed by news cameras entering 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 remaining three were later found at a nearby trucking business.
Investigators have not yet provided a motive for the attack.
San Mateo County Sheriff Christina Corpus said at a news conference that the suspect was arrested after driving into a local police station around 4:40 p.m.
He added that he had found a semi-automatic pistol that may have been used in the attack, and that he was “cooperating” with police at this time.
Mrs Corpus added that an eighth victim was being treated in hospital and was in a critical condition.
He said that this kind of shooting is scary. “It’s a tragedy we hear about often, but today it hits home here in San Mateo County.”
At a news conference, the sheriff also confirmed that the witnesses included children who had recently dropped out of school and lived on the rural property.
“It is indescribable for children,” he said.
California Gov. Gavin Newsom tweeted that he was “visiting victims of a mass shooting at the hospital when I was pulled out for a briefing about another shooting.
“This time in Half Moon Bay. Tragedy upon tragedy.”
Half Moon Bay council member Debbie Ruddock told JEE News that the victims were Chinese farm workers.
Dave Pine, president of the San Mateo County Board of Supervisors, told The Associated Press that the attacks were carried out by a “disturbed activist.”
“We are sickened by today’s tragedy at Half Moon Bay,” Mr Pyne said in a statement.
“The scourge of gun violence has sadly hit home. We don’t even have time to grieve for those killed in the horrific shooting in Monterey Park. Gun violence must stop.”
