Didn't the OP say that someone had fired on the side of his house (the room mates were there)? Sounds like this situation has already gone past 'anonymously' to 'retaliation' and that it's time to fortify the house and post an armed watch who can return fire.Keep calling anonymously. Except there is no 'anonymously' any more.
Doing anything outside the law means your creating problems for yourself rather than solving them. So, don't do it.
In fact, a strong case can be made that even suggesting on this forum to do something outside the law, or even 'inferring' or 'hinting' that there's "other ways to deal with this", which is obvious advice to do something outside the law, is sufficient to, at the least, get your LTCH yanked. Never know who's watching, heheheh...
If the allegation would be made by some Defense Atty. that they were "only shooting blanks" without spent shells, the SAME defense argument could be made WITH spent shells. So, I'm not sure of the reasoning behind it.
Try and record, call the squads, testify if you see anything.
That b.s. about "Ooo no, don't testify 'cause some times there's bad men out there and they COULD retaliate!" is WHY these dipsticks keep getting away with stuff like this. Because they figure they can scare the law-abiding.