Boing Boing had this today
I walked from the arrival gate towards baggage claim, and when I was about halfway there, all of a sudden about a dozen or more TSA personnel and private security staff appeared, shouting STOP WHERE YOU ARE. FREEZE. DO NOT MOVE. Not just at me, but all of the travelers who happened to be wandering through the hallway at that moment.
I made a comment on that post that the exact same thing happened to me.
This happened to me when i was in PDX a few weeks ago. I was leaving the secured area after getting off a plane, i was near the screeners but not yet through. The TSA people started yelling and did the same thing you described and had everyone freeze.
It only lasted a few minutes for me.
My tax dollars at work. Whatever.