Well, here is a reference to a "shoot out".
The only shoot out that I've seen clearly mentioned on the TV news was an incident where supposedly armed men "on a briedge" fired at rescue workers, and the police fired back. The first report was the 5 locals had been killed, that was later revised to 2 killed, two wounded, and others missing.
One version of this I heard in a blog was that the men who were killed were not firing _at_ rescue workers, they were firing in the air to attract the attention of rescue workers. The police then fired on them. Not sure if this is true, but it does match some television reports I've seen, in which Nawliners were complaining that they were shot at after firing guns to attract help.
I'm not sure if this is the same incident:
From Reporters Sans Frontiers
http://www.rsf.org/article.php3?id_article=14894
Police violence against journalists in New Orleans in Katrina aftermath
"A second incident involved Gordon Russell of the New Orleans-based Times-Picayune daily as he was covering a shoot-out between police and local residents near the convention centre where hurricane victims were awaiting evacuation. The police detained Russell and smashed all of his equipment on the ground. Russell was forced to flee to avoid further violence and reportedly left the city the same day."