The only other possibility is suicide.
New Orleans reported the first verified murder in the city since Hurricane Katrina. However, seventeen bodies with gunshot wounds were found in the city after the hurricane. However, the deaths "have not been listed as homicides because of obstacles keeping police from investigating."
Obstacles? What obstacles could they be facing?
Maybe the coroner cannot confirm if the victims died of the gunshot wounds? Perhaps the victims were shot but actually drowned? Perhaps the bodies were in such poor condition it is difficult to discern the exact cause of death? (Really?)
Maybe the coroner cannot discern whether fatal gunshots were self-inflicted? I might buy this excuse. If the deaths were self-inflicted they would be suicides rather than murders. And, if the bodies are decomposed enough, or water logged enough, there was no way to test for powder burns on the victims hands. However, most professional coroners can tell from powder burns at the site of the wound, location of the wound, and angle of trajectory if it is likely or impossible that a particular wound was self inflicted or not.
Perhaps, the most seasoned coroner staff in New Orleans are still among the MIAs.