Dunno about the laws in CA, but almost every state that I've lived, warning shots are a bad idea. Most civilians have the right to self defense for protection of life and limb. By the very definition of shooting over or under him, you are just using the forearm not for self-defense, but as a giant noisy warning, like an air horn.
I've seen people go to jail for firing warning shots. Don't shoot until you have to, and then put the fucker down.