I was a moderator on an other site some years ago. There was an ongoing problem with people harassing others, and the moderators had to deal with stuff. I had to ban this guy several times, for threatening other people.
He came back again and again, using hidden ISP numbers etc. He posted that he was going to kill me and rape me and several of the other mods as well as the owner of the site. This guy started his own site, with the purpose of threatening people on our site and the server company shut it down for breaking all kinds of rules. (You can't start an internet board with the purpose of talking about raping and killing people, evidently.)
Through using the FBI (because his threats were so specific and graphic) and ISP traces, the owner found out who he was, and at last contact, charges were pending. He tried to get out of it by supposedly joining the Army, but my guess is he really didn't.
There are some scary people out there.