I didn't take the time to read the whole thread, but anyone who knows me knows that my opinion of animal trainers is the 99.999% of them FAIL to respect the predatory nature of the animals they work with. I work every day of my life with animals that can kill me. I'm aware of it and treat them with the respect they deserve. When that doesn't happen, people die. This is a great example of that.
There were several things that happend wrong for yesterday's event to transpire. Fixing any one of them may have saved a life.
Putting the animal down or letting it go are bad ideas. Very rarely can captive trained show animals be released. They have no need to use this animal for shows (in water work). Let it be an educational display and keep the animal in situations where it can't kill anymore. This particular animal has a record of killing trainers.