Bones Anyone?

This morning while exiting my apartment I noticed a pile of discarded barbecue pork bones on my doormat. There was a good pile and it seems they were deliberately placed on my mat. Thing is it doesn't make sense. Plenty of dogs stomp around in the neighborhood but they do not climb the stairs in buildings and there is no reason why they would pick my doormat over someone else's. And I am positive they do not eat barbecue. The neighbors generally litter the stairway anyway with bits of sandwiches, cellophane bags, and cigarette butts strewn everywhere, not to mention old, crumbing plaster and floorboards from their apartments they are throwing away. Actually once I noticed that some one had put out their cigarettes in front of my apartment door as well. About a month ago in mid-morning someone tried to actually open the door, resembling that found on a bank vault with bolts sliding into the walls, ceiling and floor, presumably to enter but by the time I managed to look out there was no one around.

So what's this all about? I do not have any problems with the neighbors, I don't even speak with any of them and I have never argued with anyone living there. As far as I know the neighbors do not have quarrels with my landlord as I already verified. The neighbors on the third floor just above my apartment have been experiencing water leaking issues and as a result countless liters have flooded my WC, but that is their situation to take care of, not ours, although the landlord naturally complained to them several times to resolve whatever it is that is causing the seeping through the ceiling. So I don't understand what the problem is. Someone in the building is apparently disturbed and is incomprehensibly taking out his or her frustrations on my doormat, unless someone has another theory that they care to share by leaving a comment.