L473ncy, you are correct: there is a city bylaw which states that BB/pellet guns may not be discharged within city limits. The versions that I have seen do not speak to zoning or 'business' use, but they may not have been complete.
This sort of stupidity in the middle of a gang war is almost guaranteed to get someone killed or injured.
To the original poster: TALK TO YOUR PARENTS. Have YOUR parents talk to THEIR parents. If that fails, THEN go to the cops and explain the situation. I'm sure that the police would rather have a heads up than go through the public relations nightmare that could ensue.
Quick history lesson: ever wonder why toy guns in the US have orange tips? Somewhere in the mid-sixties (IIRC) a five-year old living in a tough neighborhood pointed a very realistic looking toy gun at a police officer. The cop thought the gun was real, and, acting in what he thought was defense of his own life, killed the kid.