Moron entering my apartment after 10:35 pm?

Alright, my current apartment lease ends June 29, yet around 10:35 pm today (June 11th) I awoke to some stranger unlocking my door with keys. It took him about 5 minutes to open it the first time, after which I yelled and said, "Excuse me?"

Then I walked over and locked the door again. I'm hoping it wasn't the building manager.

Ten minutes later, either the same person or an affiliated person came by and unlocked the door again. This time I saw a face and said "excuse me" once more, greatly irritated by this time. It wasn't the landlord, but I think it might have been the tenant who will move in after me (I hope). However what my late night intruder(s) did was really wrong; it was also wrong of the building manager to give the key to the tenants more than a week before they were allowed to move in if it was in fact the future tenants.