I'm writing a story, and need to know what type of hand gun would create a certain type of injury?

I'm writing a story, and in the story, someone gets shot in the back of the head. I need to know what sort of hand gun would -when held 4-8 inches from the back of the head- completely destroy the face. If possible, a gun that would -when shot in the back of the head- leave most of the skull intact, but decimate the face, leaving nothing recognizable. Any suggestions?