My guess, some kind of blister beetle, but the insect picture you show is black. Everything that I google looks brown. Looks closer to the black blister beetle, Epicauta pennsylvanica, but the pronotum is different, however, so it isn't this one. Will be watching for the answer.
hortster

I know the picture looks black, but as I described he's brown and large, almost 2 inches long, too big to be a blister beetle.

Though the image is a poor one and we can't see the antennae (or other identifying details) very well, I'd wager that you are on the mark by your guess of Prionus californicus. They are quite common.

They are also likely to be attracted to lights, as they are nocturnal. This is the time of year that the adults emerge from the ground, so more encounters will probably occur.

The larvae (giant grubs) can do considerable damage to trees, if the population is high enough.

Thank you for your answers, that is helpful!

I realize the pics are poor quality, all i had was my cellphone to take them...