I'm not American so I don't know the rules... but could they (IRS agents) not be "deputized" or whatever the proper term is and then do arrestssimilar to forest rangers/fish and game? Would that explain some of the large ammmo buys? That would be bad.
What if the "good guys" set this up as a plan for the future and they really do go after the +400k crowd. Along the lines of how they nailed Al Capone, at least it was something they got him for.
Hard to say at this stage of the game/movie.
Look into other ICLEI cities (it is nothing new) , you might be suprised.
The old style asylums, the ones for lunatics and menstruators....