My guess is that they realize it is terrorism, but they can't say that until after they catch them. An activated terrorist cell would really have people serpentining throughout the region. You would have backlashes against mosques, etc. Then, the police would be bothered with dealing with the resulting hysteria instead of trying to find these guys. It sounds as if there are enough LE in the area. Did I hear about 400? I would double or triple that number. LE has to flush these guys out while keeping the citizens moderately calm.
This is just a guess, but I believe that the minute these guys are caught, multiple cells will activate doing the same thing. Their mission is to invoke terror. With the D.C. snipers, the US has already experienced the "terror learning curve". The instant it happens in another city, citizens will immediately be as frightened as D.C. area residents. The shooters won't have to keep up the pace the D.C. snipers set. About two a week would be adequate to fulfill their mission...
So, how has everyone's day been so far? Beautiful day here. :)