A man accused of mass shootings at two locations in the Half Moon Bay area on Monday legally purchased the semi-automatic handgun allegedly used in the crimes, San Mateo County Sheriff Christina Corpus said.

Corpus held a press conference Tuesday with county District Attorney Stephen Wagstaffe, who said potential charges against Chunli Zhao, 67, were still being determined and his arraignment would likely take place on Wednesday afternoon.

"We've never had one in this county with this many deaths," Wagstaffe said. He said the case was at the beginning stage and would take months and perhaps years to conclude.

The only survivor of the attack was in stable condition as of Tuesday after undergoing surgery, according to Corpus. Seven people were killed at two locations on Monday — at Mountain Mushroom Farm in the 12700 block of San Mateo Road and another agricultural business in the 2100 block of state Highway 1. Four were killed and one critically wounded at Mountain Mushroom Farm, and three more victims were found at the business on Highway 1.

Corpus confirmed Zhao was an employee at Mountain Mushroom Farm and said that was the only connection investigators have found between the suspect and victims so far.

The county coroner's office is still working to determine the identities of the victims. Corpus said some victims were members of the migrant community in the county, which could create a challenge for identification and notification of family members.

Zhao was arrested Monday at 4:40 p.m. after parking his vehicle in the parking lot of a Half Moon Bay sheriff's substation, but he did not immediately surrender to authorities, according to sheriff's spokesperson Lt. Eamonn Allen, who said a deputy noticed the suspect vehicle. Zhao was ordered out of the vehicle and was taken into custody without further incident.

"All the evidence we have points to a case of workplace violence," said Allen, who declined to elaborate on a possible motive. He said there were children in the area of the shooting, but could not confirm that any were eyewitnesses of the shooting. All of the victims were adults.

"The coast has experienced its share of challenges," Allen said, referring to recent storms that have ravaged the county. "This just adds to that stress."

Allen said Zhao was not known to authorities before the shooting.

Corpus ended Tuesday's press conference by offering words of support for San Mateo County and those affected by the tragedy.

"My condolences to the victims, the families, the co-workers and the coastal community who is suffering greatly," Corpus said.