Originally Posted by Akula2ssn
I was limiting the scope to these kind of establishments, specifically theaters. But yes, if we want to widen the scope even more to include every public location then it's not possible. Few months ago, I was down in Long Beach, CA. Just looking out the window as I and my buddies drove to work, it brought home the enormity of the worst case scenario. The Coast Guard captain of the port has the authority to shut down a port. It has to be a very very very bad and very very very specific threat with a bunch of intel to back it up before I would see a captain of the port to even think about doing that. And no doubt every Federal, State, County, and municipal agency in the area would be tied up with just that task. Especially in the LA area which is like the doomsday scenario that disaster planners practically dream about. New York would have the same problem.
As to your point about specifically targeting theaters with extra police, apparently the NYPD is doing just that tonight.