Worst thing you ever saw at a Sports Event

[Trip]

The shitville/rivalry topic made me remember something I saw at an SEC game.

It was after a football game and the home team lost a very very close one against a huge rival. As me and my grandpa were walking out, I saw one lone away team fan just ragging the shit out of this huge group of home fans surrounding him. I then saw about 6-7 guys rush this guy and take him to the floor. One guy got up while there others were holding him down and he drew out a knife and proceeded to give the guy 10-15 jabs to the chest. Blood going everywhere, the crowd chanting it on. It was fucking gruesome. My grandpa got my ass out of there fast because I was relatively young. It was fucked up.

What's the most violent thing you have seen happen at a sport event?