What an awful mess.
It should have been self-evident that a corruptly-administered, high-crime city subjected to a disaster would descend into senseless violence almost immediately. Anybody who didn't think so, didn't spend much time thinking about humans.
Therefore, it follows that, in the event of such a disaster, you need to first impose order with an overwhelming display of force. Otherwise, all other priorities (e.g. save people from horrible deaths) become impossible, as scumbags shoot at boats carrying supplies, shoot at helicopters trying to rescue people, loot hospitals so they can't provide health care, snipe at hospitals so they can't evacuate patients, and so forth. And last I checked, all of the above have already happened in New Orleans in the storm's aftermath.
The truth is, some proportion of the city's population needs to be shot, and it isn't happening, and as a result the wrong people are dying.