Big Nog's broken arm, courtesy of @UFC
How did it happen? Well here's the complete play-by-play from the very exciting fight that went back and forth leading to that dramatic, and brutal finish:
Frank Mir vs. Antonio Rodrigo Nogueira - Round 1 - Jab by Nog gets in. Another jab lands for Nog. And again he gets in with it. Nog looks for a takedown which gets stuffed. Nogueira working him against the cage and Mir turns him. Mir gets the takedown into Nog's half guard. Nogueira gets up. Nice elbows by Nogueira in the clinch, and again. Big knee and a left hand. Noguiera landing hard and Mir drops! Nog with more punches and Mir manages to escape from a choke. Mir briefly on top. Mir takes the arm with a kimura. Nog won't tap. They're rolling, Nogeira still wont tap and the shoulder pops. Frank Mir wins by submission (kimura), round 1.