That's a couple shots with some dove shot
BBs are WAY too big to be dove shot.
It MAY be some sort of duck shot (like #6-#4 shot) but then the BBs would have penetrated the skin more. Then again, if the dog was about 60-70 yards away, the BBs only may have enough energy left to barely pierce the skin as you see here.
But I'm still leaning towards BB gun. look at the pattern on the torso. The shot appears to have come from the side and the shot on the skull appears to have come from the front.
But I may be wrong...