The only known connection between the 66-year-old suspect and the victims is that they may have been coworkers, according to the San Mateo County Sheriff's Office.
The mass killing took place at two mushroom-growing locations. Multiple victims were found in both scenes.
The victims, seven men and one woman, were Asian or Hispanic, Corpus said. Their identities will be released publicly following notification of next of kin.
"As some of these victims were members of our migrant community, this represents a unique challenge when it comes to notifications and identifications," Corpus said.
As of Tuesday, the one injured victim was in stable condition after receiving surgery, Corpus noted.
The suspect was taken into custody peacefully on Monday afternoon in the parking lot of a San Mateo County Sheriff's substation in Half Moon Bay. A semi-automatic handgun was found in his vehicle.
The Sheriff's Office said the firearm was legally purchased and owned.
San Mateo County District Attorney Steve Wagstaffe said the exact charges against the suspect have not been determined yet, while he is scheduled to be arraigned Wednesday afternoon.
"We're not going to be giving out a lot of precise detail on what was said," Wagstaffe said. "This is a case that is at the beginning stage. It has a long road to travel over the coming months and years."
"Too many guns. Semi-automatic guns and automatic rifles need to be banned, period. There's no excuse for it," said Half Moon Bay Mayor Deborah Penrose on the tragedy.
"There are lots of tragedies hitting our country right now, more mass shootings than the number of days in a month, and to hit our small town is really shocking," Half Moon Bay resident Evany Sullivan was quoted as saying in a report by NBC Bay Area.
U.S. President Joe Biden on Tuesday released a statement addressing the mass shootings.
"For the second time in recent days, California communities are mourning the loss of loved ones in a senseless act of gun violence," Biden said, adding that "even as we await further details on these shootings, we know the scourge of gun violence across America requires stronger action."
According to Biden, a federal Assault Weapons Ban and legislation were reintroduced to raise the minimum purchase age for assault weapons to 21 after the mass shootings. "I once again urge both chambers of Congress to act quickly and deliver this Assault Weapons Ban to my desk, and take action to keep American communities, schools, workplaces, and homes safe," he noted.