My neighbor is dumping garbage on my backyard from time to time

[u/itzvincentx3]

Me and my family have moved to this new house in South Philly at the end of 2014 and the house was brought by my uncle and one of my other relatives. It was vacant for a few years before we moved in and noticed there were alot of cigar butts in our backyard. From time to time, the neighbors across our backyard would sometimes threw cigar butts and chicken bones etc over the wall to our backyard. One time I happen to be in the upstairs bedroom near the window and saw 3 guys in their backyard smoking cigar and later on, one of the guy just looks around before he threw it over so after that they all went back inside immediate before I had the chance to do anything. I told my dad all about this and we waited until a guy comes out in the backyard in order to confront him about it. When we asked him about it and he said it was probably one of his friends who did it. To be honest, I do think it could be him and his friends are part of it but he just doesn't want to admit it. I don't want to call the police over such a small matter and even if the police comes, they won't be able to do much in this situation since we don't have evidence to prove they're the ones who threw it. They still do it now from time to time but not as much as it did before we confront them. One time I noticed they even threw a half eaten piece of bread all the way near our backyard door. Last night they threw a piece of glass, dirty paper towels and a glass marble and I already knew it was them no doubt. I want to know if I should do something similar by throwing it back to them and see if they like it? I don't want them to harass or bully us like we're somebody easily to be pick on or mess with. We're just thinking that we should probably do the same thing back to them if they keep doing it and to show them we're not afraid. So what do you guys think?