Just a quick thought, as recently I have had a few experiences where the owner living in the home has been foreclosed on and once the property sells they do not move out on time. I was surprised to learn the process can take up to 3 weeks to get the person removed from the home.
The police cannot do anything about it. The process is to go back to the lawyer for the lender who foreclosed on the property and have them file for a writ of possession. They are then in a position to get a sheriff and/or a bailiff involved to evict the person living there.
I have had 2 recently where the day of possession came and the new owners were greeted with people living in their home and refusing to leave. You would think with a moving truck in tow and a court order granting ownership of the property to the new owners that the police would be able to evict the person living there for trespassing. Not the case (although, I still do not understand why).
With that said, there are ways to ensure this does not happen to you. You can have the lawyer for the lender file a writ of assistance on the day the court approves the sale. This does allow the police to assist. I have yet to see a lawyer do this, but it is an option.
It is a sad thing to see a family trying to move into their new home with kids, dogs, movers etc… waiting to go in, only to have someone deciding they are going to trespass.