California Ground Squirrel

This is definitely not a gray. Western grays for one thing, typically have a bushier tail and it is usually edged in white. This squirrel also has white mottling on the body that gray squirrels don't have. The body is also robust and stocky like a ground squirrel.

How big was the tail? This seems more like a Ground Squirrel. Most of the times (not always) the busy tailed squirrels, the tails would be up and curled over when they are standing upright. I can't see the tail in this image.