California Has More Than 100 Gun Laws. Why Don’t They Stop the Worst Mass Shootings?

A 2021 study by the Violence Prevention Research Program at the University of California, Davis, found that although gun violence restraining orders had been available in California for five years, two-thirds of the Californians surveyed had never heard of them.

Dr. Garen J. Wintemute, who directs the program, said many mass shooters signal their intentions in advance, or leave hints in their planning. At any point in time in California, he said, one in eight adults knows at least one person they believe is at risk of harming someone else or themselves, research shows.

One model may be the city of San Diego, where the city attorney, Mara Elliott, has requested more than a thousand gun violence restraining orders since 2017. This month, the city requested and won the removal of a gun from an individual who threatened to kill people at a local hospital.

“I think most people second-guess their judgment. They think, ‘I don’t know who to call,’ or ‘I don’t want to bother law enforcement, it’s probably nothing,’’’ Ms. Elliott said. “Now our community knows to make phone calls.’’

Acquaintances and court records painted the Monterey Park suspect, Mr. Tran, as an embittered, paranoid and divorced loner. In Hemet, Calif., where he lived, police said he came to the station two weeks before the shooting to complain, without evidence, that he was the victim of fraud and theft and that his family had previously tried to poison him.

In Half Moon Bay, Mr. Zhao told NBC Bay Area in a jailhouse interview that he “was not in his right mind” and had felt mistreated for years at his workplace. Authorities confirmed a report that the accused gunman appeared to have snapped after a supervisor billed him $100 for a forklift accident.