Turn it in, or turn in half and keep half to finance your VERY NECESSARY move. Go now!
Nah, if he turns it in, he'll have to turn in all of it. I'm sure it's trivial for the police to get his accounts monitored after he turns in the cash, and if he starts doing a lot of expensive stuff without his accounts moving at all, they'll probably start asking some questions.
But as soon as you take it to the police, you'd better be damn sure no one knows your name when you move out, otherwise you'll still have a pissed off criminal looking for you once he's released. Personally, I'd say just put it back where you found it, and get the hell out, let someone else deal with it, be that the landlord or the next sucker who moves in.
I mean, if you were gonna keep the money, you'd probably have to do some illegal (and difficult) things to move it in a way that'd keep you safe from the criminal (i.e. bank account with fake name/ID, wire to anonymous Swiss account, etc.). It's probably just best to count it as unfortunate luck, suck it up and finance your own quick move back out of there, and just have it as a fun story to tell a few years down the line when it's well behind you. Well, and when some other poor bastard makes the news in relation to the money.

Then you can say "at least it wasn't me."