WASHINGTON (AP) - Mike Tyson's career may have ended in shocking fashion Saturday night when he quit on the stool after taking a beating in a foul-filled sixth round against unheralded Kevin McBride.

Tyson lost for the third time in his last four fights, and once again he faded badly as the rounds went on before head butting McBride in a desperate attempt to end the fight in the sixth round.

Tyson was pushed to the canvas when the round ended, his head stuck between the first and second ropes. He got up very slowly, wobbled back to his corner and sat on his stool.

When referee Joe Cortez came by to look at him, his corner told Cortez the fighter could not continue. Cortez then went over and raised McBride's hand in victory.

The 38-year-old Tyson was a huge favorite over McBride and won the early rounds. But as the fight went on, it was McBride landing the bigger punches as Tyson desperately tried to score a knockout.

Tyson was weary by the fifth round and, in the sixth round, he was penalized two points for deliberately head butting McBride and opening a cut over his left eye. The head butt came after Tyson appeared to try to break McBride's arm in a clinch like he once did against Francois Botha and after he hit him with several low blows.

In a career filled with tremendous highs and terrible lows, Tyson may have reached a new low in the loss to McBride, who came into the fight with no credentials.