JohnRM
Don't make me destroy you
He'd have to contact your ISP. Depending on how long they keep their logs, they'd be able to tell him who used the IP at that particular time.
Of course, it is very unlikely that they will do that for anybody but a law enforcement agency. Without the ISP's cooperation, he can only locate the general area in which you live.
And it is even more unlikely that this guy really wants to kill you.
He speaketh the truth!
In addition, I wouldn't fear the Nazi, anyway. These people are mostly skinny, dumb, and weak-minded little kids with a bad haircut, with ADD. Even if the ISP somehow was willing to hand out your information, this guy would likely lose interest before he made the trip. And even so, he still doesn't know what you look like in order to kill you. He'd have to kill everyone that walks into your house. That may not be comforting to you, but...yeah.
! I think you're describing AL_DA_GREAT by accident 