Well, it turns out that scenario is hard to imagine. In the days of chaos following the storm there was little coordination of any sort, let alone a concerted effort to achieve one goal irrelevant to getting people off roof tops. From TheTrace.org :
At critical points during the storm, there was no functioning state, no coordination of efforts — much less a grand plan. But the looming threat of bigger gun-grabs relies on the existence of supremely competent, and supremely malign, government forces working in perfect lockstep. They simply do not exist, and Katrina is the surest proof.