Half Moon Bay shooting suspect once tried to suffocate coworker ...

The Santa Clara County Superior Court records paint a picture similar to that of Monday’s mass shooting, the deadliest in San Mateo County history.

Investigators say Zhao shot and killed his co-workers at two mushroom farms, while injuring an eighth employee, in a “workplace violence” incident. The San Mateo County district attorney said he is planning to file charges Tuesday against Zhao, who is being held without bail at a Redwood City jail, where he was booked on suspicion of seven counts of first degree murder and one count of attempted murder.

In March 2013, Zhao worked at a South Bay restaurant. On March 10, according to Wang’s restraining order application, he quit the job. Over the next week, Wang described in court records an escalating fear about his roommate and former co-worker’s behavior.

On the morning of March 12, Zhao snuck into Wang’s room at their apartment on Greendale Way in San Jose and asked for his salary, Wang wrote. Wang told him to pick up his checks at the restaurant since he didn’t have possession of any checks.

The records do not say if Wang was Zhao’s manager or why Zhao would have asked Wang for his paycheck.

“Mr. Zhao said to me, today I am going to kill you,” Wang wrote. “He then took a pillow and started to cover my face and suffocate me.... While I couldn’t breathe, I used all my might within the few seconds to push him away with my blanket.”

After freeing himself, Wang said he called for help. He said another roommate tried to assist him, but that Zhao had locked the door to the room to keep others out.

The pair started wrestling on top of his bed, as Zhao grabbed at his blanket during the struggle, Wang said. He finally convinced Zhao to talk peacefully and they stopped fighting. The pair talked about Zhao returning to work, but Wang told him he “didn’t control that because Zhao quit,” Wang wrote.

Two days later, on the night of March 14, Wang returned from work and went to his apartment kitchen to get water when Zhao confronted him, he wrote in the restraining order application. He wanted to return to work, he again told Wang.

“If this can’t be done, this would be a bigger problem, which will not be good/pleasant for everyone. This seemed to be a threat to me and the restaurant I work at,” Wang wrote. Zhao told Wang not to be a victim and leave him no other choice, he wrote.

“Mr. Zhao said he would use a kitchen knife to split my head,” Wang said.

In his application, he summarized the week of threats and violence: “Making threats of making life difficult at work and threatening to kill me if I don’t get him his job back.”

When asked if Zhao owned any firearms, Wang checked a box indicating he did not know. In California, people under a restraining order — even a temporary one — must surrender their weapons within 24 hours. He also indicated that police were not called to respond to any of the incidents.

A series of judges extended the temporary restraining order — which forced Zhao to stay 300 yards away outside of the apartment and 3 yards away inside the unit — until July 2013. At that time, a judge turned down Wang’s attempt to extend it again and let it expire.

The son of a man who ran a now-closed Cupertino restaurant with partners told The Chronicle that Zhao worked for the business for around six months a dozen or so years ago. Zhao was let go, the employer’s son said he learned, after a co-worker accused Zhao of trying to suffocate him over a money dispute. The son had seen Zhao around Cupertino in the years following.

The son asked not to be identified, and The Chronicle is not naming him under its anonymous sources policy.

Yoyo Duan, a supervisor at a Chinese bank in Cupertino near the restaurant where Zhao used to work, said Zhao and his wife came in once a month for at least the past five years to send remittances to China. The last time Duan saw them was a month ago.

“He was pretty kind,” Duan said. “First, I was really shocked by this news. I didn’t think he would do those things.”

Duan said she once helped translate a simple insurance letter for them as they spoke limited English.

At a Tuesday news conference, investigators said Zhao used a legally purchased semiautomatic handgun to shoot seven men and one woman, believed to be co-workers. They said his rampage began at California Terra Garden, formerly known as Mountain Mushroom Farm, where he worked, just after 2 p.m. on Monday.

He allegedly walked into the business on the 12700 block of Highway 92, also known as San Mateo Road, and opened fire, leaving four people dead and another with life-threatening wounds. Zhao continued on to a second facility on the 2100 block of Highway 1, or Cabrillo Highway South, killing three people, officials said.

After that, he allegedly drove to the county sheriff’s substation in Half Moon Bay, where deputies took him into custody after spotting him in his car in the parking lot.

As of Tuesday morning, the surviving, injured farmworker had been upgraded to stable condition after coming out of surgery, San Mateo County Sheriff Christina Corpus said.

Corpus said the coroner was still working on identifying victims and notifying next of kin, which was a challenge given that some of the victims were migrants. A sheriff’s department spokesperson, Eamonn Allen, declined to release information on whether specific individuals were targeted.

“All of the evidence we have points to this being an incident of workplace violence,” Corpus said. Officials did not release additional details about a potential motive, but Allen said there were no “specific indicators” that would have hinted at Zhao’s capacity to commit a mass shooting.

Xuizhong Li used to manage the mushroom farm until selling it a few years ago. Li told The Chronicle that Zhao worked for him for 14 or 15 months, starting either December 2016 or January 2017.

Li, speaking in Mandarin to a Chronicle reporter, said he remembered Zhao as a petty person who liked to gain advantage, often at the expense of others.

“If you gave him a little more advantage, he’d be really happy and be good to you. If he feels like he has been put at a disadvantage, he will hold grievances against you and ignore you,” Li said.

Zhao would report to Li that other workers weren’t working hard enough, Li said.

“He said he cared about the company, so he would report these things to me,” Li said. “In actuality, those workers were pretty diligent.”

San Francisco Chronicle Staff writer Claire Hao contributed to this report.

Matthias Gafni, Hannah Hagemann and Mallory Moench are San Francisco Chronicle staff writers. Email: matthias.gafni@sfchronicle.com, hannah.hagemann@sfchronicle.com, mallory.moench@sfchronicle.com. Twitter: @mgafni @hannah_hagemann @mallorymoench