Those would be, of course, the LEGAL guns.
One can also get a gun permit much easier in northern California. Lots of guns up there, pistols, rifles, you name it.
One can get an illegal gun too, I suppose, from the scuzzballs and gangsters of the world.
A couple of big mean dawgs (NOT dogs) also do the trick.
I worked in SF before retiring. I can't tell you how many times I've come across co-workers illegally carrying guns without permits. In their desk. In their purse or jacket. One time I went to lunch with a female co-worker, and as we left the building she pulls her handgun from her purse and hands it to me to check it out. In public! I admonished her to keep it out of sight, as this was downtown SF. Then there were a few times guns were pulled on me in SF, and the punks were definitely not officers. One time I'm riding in a friend's car, he hits the brakes and some guns tumble from under the seat. He asks me to do him a favor and nudge them back under. The friend was a gang member that I didn't hang around with too closely. Although you can't get a permit to carry in SF, it doesn't mean there aren't lots of guns in SF! Been there, seen it.