What to do about apartment vandalism , long story but answers are greatly appreciated. Thanx?

Management here is having a door decorating contest amongst all of the tenants in my apartment building . My unit is a two-story building and there are 10 other families on my same floor , twice in the course of 9 days , my door , which has been decorated with wrapping paper and gl ornaments , is being vandalized . I am coming home , and / or waking up in the morning to find that someone has pulled the ornaments off of the door and has broken them on the floor . Twice I have replaced the ornaments , If I happen to be home and catch them myself , so help me God ! but this is going on while I am asleep or away . What to do ? Ive reported it to the landlord and I think the police dept would just laugh at me if I reported to them a matter so small . Seeing how high of a reach this is , I doubt that a small child is doing this. It is a locked lobby ,while @ home , I've been leaving the door open a few inches to better monitor hallway activity . Im a crzy prsn n u jst dnt fk w crzy ppl