Two things going on, and they're separate. One, if people, even kids, attack violently enough to cross a line of physical harm done then yes, it's a crime a yes, the apparatus of criminal investigation should occur. Jimmy throws a light punch is different from Jimmy and four friends stomping on heads.
Two, in the US (and elsewhere, this isn't unique to here) people smell the potential for rich payouts whenever something happens that shouldn't have happened, especially so if anything government-run is involved. Some people dream of falling in a Walmart or getting hit by a Post Office mail truck because they imagine the result will be millions in legal settlement. It's a combination of basic greed and the realization that most people are not going to achieve great economic success on their own efforts. Outside serendipity is an escape from cold reality.
Perhaps a third thing in this case is people want to use absolutely anything and everything as a political weapon these days, but I'm comfortable in assuming that eben without any political angle this event would still result in lawyers and cops because of the first two things. Those are far stronger reasons than mere politics.
