Holy cow, that sounds terrifying. How did you handle it? Had you already made statements prior to the threat that (in hindsight) were bait/designed to trap you?

Feds are shifty bastards. I had one come to my house. When I refused to speak, and I started shutting the door, they stuck their hand in so they could claim assault if I shut it. Fortunately I was using my hand to close it, rather than slamming it as I normally do, and I was able to stop it before it hit their hand. We stared at each other in silence for a solid minute and they left. Fucking weird.

That is creepy as hell, sounds like you had an encounter with Agent Smith from The Matrix, except for reals.