Why didn't the police come when called? Did you tell them that you thought it was management?
I'm no expert, but from my experience, if your rent is paid and you are abiding by any conditions in your rental contract it's "your" apartment until the lease ends. Management has no right to take anything, and can only enter under certain conditions (which should be defined in your lease).
I'm sure someone else will have more complete and likely better advice, so hang on...

