You know, I have even seen horses percieved to be gentle go bezerk at times. Too often humans think of animals in human terms. Animals do not think in terms of human law, only owner law. If the owner does not instill a code of conduct to an animal then he has no guidance. Even if the animal is trained, during an event of distress, it will often as not revert to animalistic behavior to survive. A human being will do the same thing at times.
I believe that in times of crisis, we humans demonstrate the ethics/behavior we've already learned and practiced. That's why it's so important to teach our kids and ourselves the proper logic and ethics *before* a crisis. I am certain that we are not limited by animal instincts.
(Semi-off-topic and part of my concerns about bioethics: The new "public health ethics" is based on the idea that there are different ethics under public health crises such as Katrina or bird flu scenarios. And so, they are practicing and setting up utilitarian rules for these conditions. I keep reminding these people that "self-" should precede "sacrifice.")