What were you using to talk to him online? If it was mIRC you can get his IP address with it. Then use that to find his internet provider (not sure how you do that but I'm sure you can do it). Then call the provider and see if you can find out the name on the account and possibly a phone number (might work if it's a local provider).
If you don't get this settled legally you could have three guys go to his house (one pretending to be blind) and put the fear of God into him by strapping his @ss to the kitchen table with his legs spread. Tell the kid that the blind dude is going to try to drive a nail into the table with a claw hammer very close to his genitalia. Wait until he starts crying like a little baby (if he already is wait until he passes out) before letting him up. Get the parts then beat the sh!t out of the little punk.
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