Did you hear the kid make a racial remark? I find that extremely unlikely but if you heard and saw the whole thing, I guess I can't say otherwise. I will find out.
I can not believe that that is what caused it. There is no way anything racially charged came out of that kid's mouth. That would take huge cojones and a mean spirit, and this kid has neither (and you'd probably have to be able and willing to defend yourself, both of which this kid would not have been).
The more I think about this, I realize I don't even have to ask if that was what happened. There is no way. No chance.
edit: There has to be a reason, I was thinking maybe he poked him in the eye or something like that when they were goofing around and he just lost it.