Roving mobs of that size are beyond the ability of most urban police forces to properly address.
Theoretically, one might be able to call out enough officers to engage such a threat, but not without enough equipment - including vehicles, weapons, tactical gear and on-site command, communications and control.
And even then, there's the risk of leaving large sections of the city without adequate police coverage.
The proper response would be for the mayor, via the governor, to call out the National Guard with armored vehicles, full tactical gear and live ammo.
But that will never happen in today's California, and for obvious reasons.
It would be "racist" and fail to address the "root causes" of crime.