I'm afraid there are many, many people in those houses and attics that couldn't get out. I heard one man say that once the water began to rise, he couldn't open any of the doors (which opened outward) due to the water pressure. He broke out a window in time to escape. Those that went into attics took a big chance too, with the only way out down into the water or cutting through the roof.
Hearing about people in their attics and the water was still rising made my hair stand on end.