The shootings come after a gunman opened fire and killed at least 11 people at a dance club in Los Angeles over the weekend.
Seven people were killed in a mass shooting at two locations in the coastal northern California city of Half Moon Bay, and the suspect was arrested after driving to a police parking lot, officials said.
Monday's shooting in Half Moon Bay, about 30 miles (50 km) south of San Francisco, came after another mass shooting in the southern California city of Monterey Park on Saturday that killed 11 people.
San Mateo County Sheriff Christina Corpus identified the suspect as Chunli Zhao, 67, and said he worked at one of the shooting locations.
The suspect was cooperating with investigators, but a motive had yet to be established, Corpus said.
The Sheriff’s Office first received reports of a shooting and found four people dead from gunshot wounds and a fifth injured person at the first scene.
Shortly thereafter, officers found three more people dead from gunshot wounds at a second location nearby, Captain Eamonn Allen said in a news release.
As the new tragedy unfolded, detectives at the southern end of the state were still probing what drove an elderly Asian immigrant to shoot dead 11 people gathered in celebration at a suburban dance hall on Saturday - before taking his own life as police closed in.
It was the worst mass shooting in the United States since a teenage gunman in Uvalde, Texas killed 21 people at an elementary school last May. All but two were children.
News of the second mass shooting in California in less than 48 hours spread ripples of shock through the state, which already has some of the strictest firearm laws in the United States.
Governor Gavin Newsom, who had earlier on Monday been in Monterey Park where he lashed out at federal inaction over guns, called it another "tragedy".
"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," he tweeted.
Chunli Zhao's driver's license photo has been released by the San Mateo County Sheriff's Office. San Mateo County Sheriff says that Zhao is currently being interviewed by authorities. pic.twitter.com/hEizuizVzG— Tori Gaines (@ToriDoesNewsNow) January 24, 2023
Half Moon Bay is a small coastal city with agricultural roots now home to about 12,000 people.
The city and surrounding San Mateo County area are known for producing flowers as well as vegetables like brussel sprouts.
The county allows cannabis farming in certain areas.
It’s a majority white community, and about five percent of the population is Asian, according to Census data.
There were 38 mass shootings in the US in the first 21 days of the year, according to the Gun Violence Archive, which describes a mass shooting as four or more people shot or killed, not including the shooter.
WATCH: “This kind of shooting is horrific, it’s a tragedy we hear about far too often, but today it’s hit home here in San Mateo County,” Sheriff Christina Corpus said in response to the mass shooting in Half Moon Bay, California. pic.twitter.com/cDskH78GmW— IT’S TIME FOR JUSTICE (@LiddleSavages) January 24, 2023