Nothing. CA can't get much worse, the guy was probably a felon and thus PP so ignored the zillion laws, etc. Bad people do bad things at times and the public is realizing the laws don't work except for the criminals to disarm the public.
Was the gun loaded with a 30 caliber clip? Was it a ghost gun? Was the mag release finger actuated or a bullet button? What type of barrel shroud was he using? Did he have a kydex grip cover or was his thumb able to tactically wrap around the pistol grip? Maybe he used a flash hider and so the other cops weren't able to locate him after his first shot! Had he been using an m1 garand the outcome might have been different.
Willing to bet that if CA banned guns absolutely and there were still shootings, they'd still try to pass more laws. They'd make it retroactively illegal to have ever possessed a gun, and the moonbats who used to have guns would be stupid enough to vote on that bill and get all their asses thrown in jail.