I am a dog trainer, pet socialite, in a large apartment community. You might want to check your lease for rules about laws on leashing, disruptive behavior and not picking up after their pet. These rules are also LAWS that can be enforced by animal control agencies. There are very stiff fines for these offenses. Of course, I would prefer to talk to the person and offer them the bags to use to pick up and maybe give them a name of an inexpensive dog trainer that would be willing to give them a few pointers on living in a community setting with others that have dogs. That way, EVERYONE is following the rules, so we can all live in harmony with each other. It's always better to take the high road in these situations. In my many years of experience throwing gas on a fire resolves nothing. It's unfortunate the LACK OF EDUCATION ON THE OWNERS PART. People like this should not even own pets!!! That's just my opinion. Good Luck.