Wouldn't surprise me a BIT if the Fascists errr FBI were out threatening people.
I bet the Feds were hoping the dudes said something incriminating (or something that could be twisted into something incriminating, Feds love to falsify 302 interviews), and are discussing the interview with a shit for brains AUSA on what charges can they can smear the guys with.
Moral of the story - Never talk to Feds unless your lawyer is there, period.