Chunli Zhao, 66, was booked on suspicion of seven counts of murder and one count of attempted murder, jail records showed. He was being held without bail and scheduled for a Wednesday court appearance.

Authorities believe Zhao acted alone when he entered a mushroom farm in Half Moon Bay, California, and opened fire, killing four and leaving another seriously wounded, San Mateo County Sheriff’s officials said. He then drove to another nearby farm where he had previously worked, and killed another three people, said Eamonn Allen, a sheriff’s spokesman.

Officials have not yet released the names of the five men and two women who died, nor the one man who was injured. Some were Asian and others were Hispanic, and some were migrant workers.

Servando Martinez Jimenez said his brother Marciano Martinez Jimenez, who was a delivery person and manager at one of the farms, was among those killed. Servando Martinez Jimenez said his brother never mentioned Zhao or said anything about problems with other workers.

“He was a good person. He was polite and friendly with everyone. He never had any problems with anyone. I don’t understand why all this happened,” Martinez Jimenez said in Spanish outside his Half Moon Bay home.

Marciano Martinez Jimenez, 50, had lived in the United States for 28 years after arriving from the Mexican state of Oaxaca. Servando Martinez Jimenez said he is working with the Mexican consulate to get his brother’s body home.

Allen declined to answer questions about whether Zhao had any previous criminal history, saying, “there were no specific indicators that would have led us to believe he was capable of something like this.”

But would not have been Zhao’s first fit of workplace rage, the San Francisco Chronicle reported. In 2013 Zhao was accused of threatening to split a coworker’s head open with a knife and separately tried to suffocate the man with a pillow, the Chronicle reported, based on court documents.

The two were roommates and worked at a restaurant at the time, and the man, identified as Jingjiu Wang, filed a temporary restraining order against Zhao that was granted but is no longer in effect. Wang could not be immediately reached, the Chronicle reported.

The sheriff’s office identified the first shooting location as Mountain Mushroom Farm. But California Terra Garden took over the business last year, company spokesperson David Oates said. He did not know how long Zhao worked there, adding that he was one of 35 employees who had stayed on when ownership changed. Oates declined to provide details of the four slain workers.

The site of the second shooting was nearby Concord Farms. Owner Aaron Tung said in a statement that the farm was waiting for more information before it could comment.

Half Moon Bay is a small, laid-back, coastal and agricultural city about 30 miles (50 kilometers) south of San Francisco. Its sweeping views of the Pacific Ocean make it a popular spot for hikers and tourists, who flock there to surf and for an annual giant pumpkin festival.

Several farmworkers and their families lived in mobile homes at the the mushroom farm where the four died and had been relocated to hotels and offered mental health and other support after the shootings, said Half Moon Bay Vice Mayor Joaquin Jimenez. He said the farm employs 20 to 30 Chinese and Latino workers, some of them in the country without legal permission.

“There’s a lot of fear,” said Jimenez, who is also the farmworker program director for the Latino advocacy group ALAS. “So for them to come forward to ask for help is going to be very difficult,”

Thousands of farmworkers are employed in the broader San Mateo County, an area known for growing mostly flowers, peas, Brussels sprouts and fava beans. There are a few small mushroom growers in the area, said BJ Burns, president of the San Mateo County Farm Bureau.

California was still reeling from an attack in Monterey Park, just outside Los Angeles, that killed 11 and cast a shadow over celebrations of Lunar New Year, an important holiday for many Asian American communities. Authorities are still seeking a motive for the Saturday shooting.

“For the second time in recent days, California communities are mourning the loss of loved ones in a senseless act of gun violence,” President Joe Biden said Tuesday. “Even as we await further details on these shootings, we know the scourge of gun violence across America requires stronger action.”

The new year has brought six mass killings in the U.S. in fewer than three weeks, accounting for 39 deaths. Three have occurred in California since Jan. 16, according to a database compiled by The Associated Press, USA Today and Northeastern University. The database tracks every mass killing — defined as four dead, not including the offender — in the U.S. since 2006.

At an afternoon news conference, Gov. Gavin Newsom said he met with Chinese farmworkers who heard the gunshots. Speaking through a translator, they said it was hard to comprehend what was happening, he said.

“They had never heard a sound like that,” he said.

The shooting was likely to leave some in the community fearful and searching for other work, he said.

“The trauma and the damage, the devastation, is felt for generations in some cases, communities being torn asunder no one feeling safe,” Newsom said.

The shootings in Half Moon Bay and Monterey Park followed the killing of a teenage mother, her baby and six others at a home in California’s Central Valley on Jan. 16. Officials discussing the investigation mentioned a possible gang link to the killings.

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Associated press writers Jocelyn Gecker and Janie Har in San Francisco and Sophie Austin in Sacramento, Calif., contributed.