I certainly do not know if this is correct but have been told that the poker hall of fame shows the hand with this account:

On August 2, 1876, Wild Bill entered a poker game in a saloon in Deadwood, Dakota Territory and for the first time sat with his back to an open door. Jack McCall put a bullet through the back of Wild Bill's head at 4:10 p.m. His card hand held an ace of spades, ace of clubs, two black eights - clubs and spades - and the jack of diamonds. This became known as aces and eights - the dead man's hand.

Someone who has been there could probably confirm whether or not this is true.