I've read somthing on this already for a similar case like this and how to handel it, going up to them and asking what there problem is ok, but this magazene article outlined what you should do. Basicly you let them make the first move and respond with only as much force as there using - example: they push you, you are then allowed to push them back, if they punch you - your allowed to punch them back - if they start beating on you as hard as they can the your allowed to without using any lethal techneques - if they pull out a gun or knife or other weapon that could theorecticly kill you then your allowed to pull out all the stops. The point of this is that in court you can always say THEY were the one that started it and that you weren't the one that escalated the fight and made it more deadly. If you can prove that you were not the one that threw the first blow the you should be fine. Thats just my two cents on the issue.