These people live across the river from the flooded portion of New Orleans. There is no reason for house to house searches and presumably the water and sewer systems are totally separate from flooded New Orleans. They will probably have electricity restored much earlier than in the flooded areas, so Algiers is semi-liveable provided the looters and arsonists can be kept away.
These vigilantes seem determined to stay until after the bad guys are rounded up and their homes are secured.
It really bothers me to see the cops going door to door prying open doors, marking walls, and then leaving the homes open and unguarded for the looters.