when you call in they aren't going to search you, you don't even have to leave your name, just call 911, say what you saw, and then say, I am not going to stay around here, but someone should know.
I know that some people would prefer to not be in a position to talk to the police, but if they came fast enough possibly others would chime in and they would have more information to deter this type of behavior.
The other thing that coems to mind is that if we ignore this type of behavior in our park and the people that did this may think this is an easy place to do that, so they come back.....I don't want them in my park while I am playing with my 4yr old or 11 yr old, would you?
Keep them the F*(& out, make it known that we as people that enjoy the park are going to tolerate this type of behavior in our park.....
Safety first though, get yourself in the duck and cover mode and take care of yourself, but if I were the person that got lightly hit by at Dick Cheney type blast, I would still want the people apprehended......