DHS has lots of assets to throw at a situation like this, but the Federal Protective Service's (absorbed into DHS under George W. Bush, IIRC) presence is not unexpected.
Is it all an elaborate ruse, intended to catch us off-guard? We'll know soon after the hollow-points start flying.
Well, one thing Obama has not put into place yet is the civilian security force that was to be equal to the military.
But he has two years left.