Nothing desperate about it.
They could have left on Friday and WALKED to safety.
You undoubtedly missed the discussions of those issues last week.
Tons of people felt they couldn't leave, for various reasons. Many simply didn't believe it would be as bad as the authorities were telling them. Heck, the authorities had been wrong many times before Katrina.
So, for whatever series of reasons and events, a number of people were then facing nothing but bad choices WRT theor pets. At that point, what choice would you have made?