The killer whale named Tilikum, who was involved in the death of at least three humans, is dead. You can read his obituary here:
I have seen the documentary "Blackfish". I didn't think it was all that great a movie, but it got the point across.
Whales and dolphins are intelligent creatures. I think it is cruel to capture such animals and keep them in tanks for our entertainment, just as it was cruel to hunt down and kill their cousins to provide oil for our lamps.
But then again, we are a species which starves, blows to pieces, or otherwise wantonly kills even our own, often for no reason at all. Tilikum may have been a killer, but most of us are no better than he.
RIP, big guy.
By the way, the robots and AI which we are creating will be even more intelligent than whales and dolphins. You think maybe some day they will kill humans, too? You better believe it.