I don't think they are going after an individual; it seems they are going after the leader of the Senate. First it was Daschle, now Frist.
Actually, he took Lott's job.
No, I just think it's just the building in general. The zip, room no. might match with one of the original anthrax letters. Do we know that this was addressed to a particular person, with particular writing, etc?? If perhaps it's the same folks who did the anthrax, I'd say they would duplicate the original working plan with a few innovations.
They're really not telling us much.