My question involves real estate located in the State of: Virginia

I would like to know what the legal terminology for this situation. A real estate agent rented out a property that he had a sales listing for. The owner did not authorize or know this was happening until the neighbors called to tell him that people were living in the house he had for sale. What would this be called so I can do some more research in the legal dictionary, law books.

Am I correct in assuming this would be a criminal offense?