Annoying Neighbor

We have a very annoying neighbor. They live right next door. During midnight, you can hear a lot of shouting, screaming, squabbling and I dunno exactly what was going on. It's really the opposite during daytime as I would find them very discreet... as if trying to shun away from the owner of the house whom they owed 6-months-worth of rental payment (and counting...).

What's annoying also is that whenever I chanced to see them or if they happened to be around during the broad daylight and not able to get inside their house, they kept on banging the roof outside (using their umbrella) - creating such a noise! Why can't they just put a doorbell on their house?!

The owner of the apartment is my FIL. He is nice to them but this neighbor of ours was abusing his kindness. Other neighbors in our vicinity are criticizing them, too. Well, if they don't want to be discriminated (like they claimed to be), they should also do something about it rather than tainting their race (or whatever they call it) with such an image.