Richard Mosby was a young, hotheaded Immortal. In the year 1889, he was in Sweetwater, Montana where he encountered Okajutin, who had had a few drinks too many after losing a poker game.
Seeing an opportunity, he forced his way in Okajutin's room and shot him, and then beheadeed him before he could recover. Not exactly cricket as far as the accepted Rules go, but not unprecedented.
Mosby's current status is unknown.