This is the exact mission training films that were captured in Afghanistan depict. Perhaps we have seen a test run. No reason this won't work in any populated metropolitan area--to some degree it is surprising that we have a description of the shooting van and occupants.
You assume these guys are Arabs--the Hispanic lable is just an effort to be Politically Correct.
As depicted, the van is supposed to shoot from a significant range (600-900 yards) and with a silencer (the 5.56 NATO round is not very noisy anyway); it is pretty difficult to identify the source of the shooter.
I also have some difficulty thinking about what I would do to respond if I were standing there watching it happen with my own M-14 or riot gun--if you were in range, you might shoot at tires on the van.
If they dispatch fifty van teams around the country, what do we do about it and how long do we think it would take to shut them down? Bet this van is no longer white but now yellow, or orange, or blue or some other color. No reason they need this big a van--could be done with a minivan or pickup--the idea is to give the shooter a stable platform; in some of the training films, the shooter was using a pickup with a canopy.
They could dispatch 100 of these for a capital investment of $50,000 and 200 men exposed; we would never catch all 200--they might have a few casualties but probably not many.
If the government is going to continue to deprive us of our own weapons for self defense, what are they going to do to protect us against direct armed attacks?
For all intents and purposes, nothing.
If they were going to do anything, they would have already started work on closing the borders. Has that happened? You know the answer to that one.