Just imagine this is a classic plan for phase one of a terrorist attack: Render the target blind. None of the defenses are operational. Thousands of people are trapped in restricted space without directions about how they can find an exit.
As chaos spreads nobody knows who turn to for information. The communications blackout is as complete as the power blackout.
Given this situation a small band of suicide bombers could roam freely and commit mayhem and massacre on an unprecedented scale.