According to Frank M. Wynkoop, the son of Edward Wanshaer Wynkoop in his pamphlet, Intimate Notes Relative to Col. E. W. Wynkoop by Frank M. Wynkoop (a son):

    "Wynkoop was in Deadwood City and actually sitting in the game with J. B. (Wild Bill) Hickok and others when Bill was killed by Jack McCall, who had come up behind Hickok and shot him in the back. McCall was later hanged for the murder in Yankton."

    The story of James Butler Hickok and his murder in Carl Mann's Saloon No. 10 in Deadwood, South Dakota is a pretty familiar one to most students of the old west. He died holding a hand consisting of a pair of Aces and a pair of eights that has since become famous as the "Dead Man's Hand." To read the first newspaper report of this famous incident I suggest you head over to the following website:

The Murder of Wild Bill Hickok.

    On August 2, 1876 at about 4 p.m., he joined a poker game in Carl Mann's Saloon No. 10. The other players were Charles Rich, a gunman in his own right, Con Stapleton, Carl Mann himself, and Captain Willie Massie, a Missouri steamboat pilot.