Those deaths, from what I've read, did NOT occur in the Convention Center or the Superdome. In the absence of police presence there were several murders in NO, not unlike any other weekend in the city. There were rival gangs who were killing each other, and I daresay a murder or two, the idea of which had been festering, which found a convenient situation.
In the story i saw, it said one of those bloody corpses belonged to an elderly person. Who knows? I KNOW the media will LIE in a heartbeat to get a sensational story out there, yet it is also well-known that the NOPD has a lot of "bad seeds" and they probably would prefer we not know that they were not protecting folks.