Return of last month rent

[Horrified Landlord]

I own a 2-br condo, and rented out 1 room to a professional guy. He looked quiet and kept to himself most of the time, and I seldom saw him. One night I came back very late and was horrified to find there was an orgy in my living room with some of the wierdest people I had seen. I told the tenant that this is unacceptable and he cannot stay here any longer, and that I need to talk to him the following morning. In the morning he had left with a lot of his stuff leaving me a note that he would come back for the remaining stuff on the wekend, but came in after that when I was at work. He took away his belongings and left the keys on the table. I found from the trash that he was smoking in the unit and doing drugs as well.
(I still have retained the stuff and his note)

He was on a month to month lease, and I have the last month's rent still with me. Am I obliged to return it under the circumstances?

 

[Moe from MO]

I would not, and I'd let him sue me -- and then tell him you'd turn the stuff over to the police.