Comcast security please contact me off list

I do some protective service work, one client is the head of a Washington
D.C. NGO that faced a credible death threat last month. Tonight I received
information that the source of this threat traced one of the NGO's
volunteers to her home address via Comcast IP, and the location is a
relatively short drive away from a man who was arrested last month for
criminal harassment almost five hundred miles from his home.

  I have some genuine concerns for the physical safety of this Comcast
customer, and I'd like to talk to someone immediately. We've got an annoyed
FBI agent who will confirm the back story on this Monday, but the subjects
know they're under some sort of investigation and I'm afraid of what might
happen if further info leaks over the weekend.

  This is a junk box for me - nrauhauser at gmail is the address I check

Then your FBI agent should probably go through the channels
they have to speak to Comcast, especially if it involves a threat to
life and safety. Asking on NANOG for a Comcast contact to give you
customer information (which is what it seems like you're asking for)
probably isn't going to help and makes it look more like you're trying
to social engineer some information than trying to help someone.