I think that requires a lot more work and thought than slapping a "criminal" label on the guy and giving him the same treatment as a serial car-jacker, drug dealer, etc. because they all share that same "criminal" tag.
That being said... yea of course he would need to keep his wits about him and use some moxxy when it comes to spotting some additional theft/scam like "Ok PayPal me for the hard drive so I can make the backup" -- I'm not encouraging the guy to be half retarded -- but stopping the conversation after the first sentence and filling it full of pre-conceptions because the guy with the laptop is a "criminal"... I can't get on board with that.
At least talk to him and give him a chance to prove he's a dirt bag shithead first :)
In this particular case, I think a non-typical response would yield better results than a black-or-white/militaristic response of trying to get the cops to do something, but that's just my 2 cents.