When I saw the helicopter video of the Biloxi area and all the destruction then heard that only 100 or so were dead, I assumed that most people left before landfall. I hope what your friend saw was isolated to his area and not widespread...
MSNBC quoted the state of Mississippi as saying they estimated only 1/3rd of the permanent residents of Biloxi evacuated before the storm.
There are a lot of people on the Gulf Coast and in Florida who either had never been through a hurricane or had lived through the mild ones and believed the worst could never happen to them.
I can't fathem, though, people in communitites like Bay St. Louis and Waveland would not know what a terrible storm was headed their way even if all the talk was about New Orleans. These two Mississippi towns are almost due north of New Orleans and would surely get the worst of it even if Katrina had stayed due north. You would think people would have the sense to get out.
I suppose one factor I hadn't figured on is how many elderly and retirees live in these areas and they don't leave no matter what because, in their minds, their home is all they have. So sad they felt compelled to die with their homes rather than flee.
I bet you will find a large amount of the dead will be elderly who even couldn't or wouldn't move out of the storm's path.