Hi Deer
It goes without saying that if you’re sharing a common area with other people, you must be mindful of how you use it. Definitely do NOT leave your hunting trophies out there for your neighbors to encounter. This OP’s neighbor not only collected severed deer heads but also kept them in the common area.
Even though the OP has tried to get him to stop and called the health department and police, nothing has actually been done about it. We can’t even imagine how unsettling it must be to walk past a bunch of severed heads every time you’re in that space. Ugh!