If you've got a horse that is acting up in the warmup ring, and I don't mean just little things, I mean like behaviors that could be dangerous to the horse, rider, or other horses and riders, the horse should not be entered in the class. It's better to miss one class than to have fines and injuries to worry about. And not to mention, if you are showing at this level, then you should have enough common sense to pull the horse from the class and prevent stuff like this from happening.
This was a very scary situation, and it is very lucky that no one was severely injured.
It must have been very terrifying, and I also agree that the announcer did a great job in trying to control the situation.
~Kait & Mark~