Comms, there were a LOT of LEOs from other parts of the country there and an order was given to confiscate private firearms.

‘New Orleans Mayor C. Ray Nagin ordered New Orleans police and other law enforcement entities under his authority to evict persons from their homes and to confiscate their lawfully-possessed firearms and Superintendent of Police P. Edwin Compass III announced that anyone with a weapon will have it confiscated… that only law enforcement will be allowed to have guns’
http://www.nraila.org/media/PDFs/NAGIN_complaint.declaratory.injunctive.relief.pdf

Guns to be returned: http://www.nraila.org/Legislation/Read.aspx?id=2057

One of the notes from the NRA page related that the confiscation left the citizens at the mercy of "roving gangs, home invaders and other criminals".
I think those groups, and even your neighbors who think you may have something that they need, are the ones you will need to be prepared for if the situation gets bad enough where there is an emergency that overwhelms the government agencies in the area.

Katrina was a good study of what may happen. Just as you may train to improve your skills, criminals train to improve theirs.