Did shamu the orca whale attack his trainer?

Stress or distraction from the training or the whale thinks the trainer was a toy.

Stress and boredom, swimming around in a tank instead of open ocean, doing repeated tricks for the price of a fish instead of hunting using their natural instincts. They were never meant to be kept like pets for our entertainment, they are intelligent creatures with a mind of their own, eventually they will snap. It is just tragic that a trainer lost their life, all in the name of entertainment and making money.