it seems you all are retarded
if you know his IP and/or the IP of the server he sent it from have unixmad call up the ISP for that IP ask around get in contact with the owner of that server and then look in their logs for sendmail crap and then they find his IP contact his ISP get a bit of info call up FBI (I think) and also have them shut down his internet
I personally have had internet taken from script kiddies, I own servers and if they try to do anything I just call up their ISP and a few minutes later they are gone