California has hurdles to clear (universal background check law, a 10-day waiting period, limits on handgun purchases, a microtracking system, a personal safety test, a ban on assault weapons, a minimum age to purchase of shotguns/rifles, red-flag laws allowing police to confiscate guns). I guess it's subjective, but I think these laws are fairly lax. Given those laws, how hard is it to actually obtain a firearm? It's pretty easy! So I'm not sure what kind of effect you're expecting from these laws...
Also, whenever a mass shooting occurs, by definition the currently enacted laws failed to prevent it. The same can be said anytime there's murder, theft, rape, terrorism and so on.