General Discussion

And no, it doesn't take anything specialized–one high-power bullet is more than adequate. Look up videos of people shooting watermelons. Come to think of it, the film scene was done with a fake skull stuffed full of ground meat and a shotgun blast from behind, not an internal explosion.

FWIW I don't think a true professional would have put the bullet there; at that range a real sharpshooter can be precise to under half an inch. The impact would have been a bit farther up and back, just at the base of the skull…that vaporizes the medulla oblongata, what snipers call "the apricot". As Maru has shown, that was definitely *not* hit or else he'd have displayed instant flaccid paralysis, limply dropped, rather than either of the traumatic brain damage responses.