The US state of California is reeling from its third mass shooting in eight days after a man shot dead seven former co-workers south of San Francisco.
The attacks took place in the coastal city of Half Moon Bay. Some of the victims were Chinese-American.
Suspect Chunli Zhao, 66, was arrested after driving to a police station.
It comes as the state mourns the deaths of 11 people in Monterey Park - about six hours south-east of Half Moon Bay - during Lunar New Year celebrations.
And just over a week ago, six people including a teenage mother and baby were killed at a property in Goshen, central California.
In emotional remarks at a news conference in Half Moon Bay on Tuesday afternoon, California Governor Gavin Newsom said he's grown weary of having to "say the same things we hear again and again" in the wake of mass shootings.
"What the hell is wrong with us that we allow these weapons of war and large capacity magazines out on the streets and sidewalks?" he asked. "Why have we allowed this culture, this pattern, to continue?"
"Only in America do we see this kind of carnage," he added.
The latest bloodshed to hit the state took place at two locations around the Half Moon Bay community in what officials have described as instances of workplace violence.
Four victims were discovered at a mushroom farm, while the other three were later found at a nearby trucking business. An eighth victim who was transported to hospital is out of surgery and in a stable condition, San Mateo County Sheriff Christina Corpus said at a news conference on Tuesday.
The victims were five adult men and two women, Sheriff Corpus said. All of them were agricultural workers, Half Moon Bay Mayor Deborah Penrose told CNN on Tuesday.
The suspect was a resident of Half Moon Bay and employed at the Mountain Mushroom Farm, Sheriff Corpus said.
"The only connection between the suspects and the victims is that they may have been co-workers," Sheriff Corpus said. "All of the evidence we have points to this being an instance of workplace violence."
The operator of the farm - California Terra Garden - later confirmed that the suspect lived at one of the two locations where people were killed.
The suspect is due to be arraigned on Wednesday in Redwood City, California, according to local US media outlets.
Alicia Ortega said her partner, Martin Martinez, a manager of the mushroom farm, was shot and killed in the attack.
The last time she spoke to him was in "the morning, when he [went] to work", she told KPIX, a local affiliate of CBS News, the BBC's US partner.
A number of children who had recently been let out of school and lived on the rural property saw the attack take place, Sheriff Corpus said.
"For children to witness this is unspeakable," the sheriff's office said.
After carrying out the killings, the suspect drove to a local police station where his arrest was caught on camera.
US news channels showed the suspect being pinned to the ground and arrested by police.
He used a legally purchased semi-automatic pistol, Sheriff Corpus said.
San Mateo County Board of Supervisors President Dave Pine told the Associated Press news agency that the attacks were committed by a "disgruntled worker".
In a statement, President Joe Biden said he was praying for the victims and called on Congress to pass legislation reintroduced this week by Democratic senators that would raise the minimum age to purchase assault weapons in the US to 21.
Just hours after the attack, seven people were injured and one person was killed in a shooting in Oakland - about 40 miles (64 km) north-east of Half Moon Bay.
The Half Moon Bay attack is the 37th mass shooting in just 24 days, according to Gun Violence Archive.
Even as details of the deadly attack in Half Moon Bay were coming in, detectives in the south of the state were still hunting for a motive for the killings in Monterey Park.
There, an elderly Asian immigrant murdered 11 people in a suburban dance hall, before killing himself as police closed in.