From NESW Sports, "This youtuber was sitting near the front row, and he caught an awesome vid of the end of this fight that will, at the very least, be talked about for some time. Mayweather wins by knockout. But how did we get there?"
UPDATE: Video was pulled from YouTube. Above is a short clip showing the headbutt, hug, and knockout.
Video: Best View of Mayweather vs Ortiz Cheap Shots [NESW Sports]