[Derek can;t quite manage to turn the video off when he answers, and his voice is muffled badly. But he does try to keep out of view of the camera. Whether he succeeds of not is up to his unsuspecting audience.]

...Felines, canines and bears sometimes will crunch their prey's skull if they can get their mouth around it. But they usually break it open enough to get at the brains. If that was done by an animal, it was either scared off the kill almost immediately, or it was sick.

Only other thing I can think of that would leave a killing wound like that would be a vampire, but they don't usually bite through the skull. Does the body still have blood?