I think it is a big problem with him being a member. Whether he has been there for a while or just became one. What do you think would happen if a kid was walking around late at night and wasn't being real noisy, and did get close enough to see something like that? Hopefully the kid would tell someone about it. I believe it would still be good to let the management know. If the management is good, then maybe one night they will sneak out late and see for themselves what is happening. Would be good to have them aware of it though. I would advise you call them when you have some time and explain what happened that night. It would be good for them to check into it, or eventually they may be liable for a lawsuit for allowing it to happen. So, I hope it goes well for you.