You remember a free -- that adorable killer whale who long for freedom until -- little boy came to save him. -- turns out it may have been more than just Hollywood's political license to think a... See More
You remember a free -- that adorable killer whale who long for freedom until -- little boy came to save him. -- turns out it may have been more than just Hollywood's political license to think a magnificent mammal like that might chafe against captivity. That is the belief held by a group of filmmakers behind a new documentary called black fish who argue that these apex predators which are no real threat to humans in the wild. Maybe driven to violence against us when they become tourist attractions. Here's ABC's Lindsey Davis. This seems seems so joyful. -- SeaWorld trainer dawn Rancho performing with Telecom spectacular killer whale she -- laced with him. Bonds they lie down together in shallow water. And then something goes terribly wrong. This whale grabbed her pulled them a lot of till it come. 121000. Pound 22 foot long killer whale kills the forty year old trainer igniting controversy that still playing out today. I don't understand why a killer whale would. Essentially bite the hand that feeds it -- you know his trainer so you know presume that they have this loving bond. Get every helicopter -- is a filmmaker whose latest documentary black fish examines just -- to a common branch teller arrived at the -- moment three years ago. And -- question should killer whales be held in captivity. One of the things that shocked me the most was how violent and prolonged and ones that is the stuff of nightmares. -- whose death was particularly shocking because she was one of the most gifted an experienced trainers at sea world -- was. The poster child for -- world. She's beautiful she's blonde and more than all of that she was -- top top trainer. But should this incident have been a surprise there had been four deaths involving killer whales in captivity -- -- has been associated with three of them. First someone who's never met him at a spent any time -- and how would you describe. Carlisle is until it that was a real puppy dog that tennis shoes and how naive I was. To -- come is the patriarch of roughly half of all the killer whales at SeaWorld parks. The crown favorite. What does the -- that causes people just fall in love with these animals there's such impressive animals to look at. The capacity of those animals and intelligence when you look into their eyes you know somebody's home they're spectacular. In the wild the animals -- -- reached tightly bound communities. These big families and they have life -- very similar to human life spends. The adult offspring never leave their mother's side. True. -- killer whales have never been responsible for loss of life in the wild that's the human life. This -- true there's no documented case of a killer -- ever killing. Anybody in the wild it's only in captivity. Where these incidents that happen. Copper -- traces what she calls a forty year experiment back to the beginning -- a really exciting thing to do and so. Everybody wanted to do it the hunts from more than forty years ago to capture the first killer whales for the first marine parks he had speedboats they had bombs -- were throwing water. -- -- -- -- -- -- The animals intelligence was readily apparent. -- adults we. -- -- went east in two cul-de-sac and the boats followed them thinking they were all going that way while the mothers whose babies. -- north -- the capture came to an aircraft. They have to -- -- career eventually and when they did. -- -- teams alerted the boats and fishing boats we've -- nets can stretch across. So none could leave and then they could just pick out the young ones. The hunt separating young chiller whales from their mothers destroying their social connection. There's usually -- thing -- and -- he is about two years old -- was captured off the coast of Iceland in 1983. You know he -- taken from his mother. It is very young age and then he's dumped in this park called -- in the Pacific and is beat up on consistently that. Night -- come and the two other killer whales were kept in a holding pen just twenty feet across and thirty feet deep there. It didn't feel good it just didn't closing that door on him. And knowing that he's walked in there for the -- -- designed. To staff and -- -- it was at sea land of the Pacific in 1991 -- to look at what's responsible for the death of the trainer for the first time. The whale grabbed her back foot and pulled down -- It was the very next year -- to -- and arrived at SeaWorld in Orlando to the delight of tourists who knew nothing about his past. But he 1999. A second death when a park visitor managed to stay after the park closed. Would happen next is unclear the next morning he was found draped across till it comes back dead from hypothermia. It's not known what role if any to a -- -- his death but fatalities aren't the only concern. The very behavior of the killer whale isn't 100% predictable from 1988 to 2009. Before dawn brand -- death. SeaWorld generated 100 incident reports of killer whales and gauging and undesirable behavior. Including nearly a dozen that involved injuries to trainers. Swimming. -- 8000 pound killer wells. As a human being our bodies are not designed to do that but he would also had injuries related to aggression. With the whales for sure. In one incident the trainer made the mistake of putting her foot on and off a killer whale. Watching the video knowing -- your stomach -- because you know what's probably gonna happen. Which grabbed when you see her just ripped from the game and you hear her just scream out somebody help me. The trainer was eventually released but not before having her arm badly broken. She's very lucky to be alive that's for sure tragically Don brand show did not have a similar outcome to talk about -- -- like she knew she wanted to work with the animals and -- us victory. We embarked on the sort of forty year experiment here the marine park experiment bank the results of this forty year experiment -- that we can just never. And virtually give them what they need. And it's actually very dangerous for us to try the government. Agreed in the wake of French -- death. -- undertook an investigation of the incident. And ordered SeaWorld to keep trainers further away from killer whales even placing them behind barriers ending the intimate -- dramatic acrobatic work that once thrilled audiences. Sea world continues to appeal the decision and says OSHA has a fundamental misunderstanding of how to properly and safely care for and work around these animals. SeaWorld says they were deeply saddened by the death of -- And -- 2010 the company has voluntarily implemented significant changes to the training protocols for its killer whale program. They're proving to be safe and effective. -- world believes that marine parks plays a crucial role in society. Displaying marine mammals like killer whales provides an -- valuable educational resource to the public they point out that -- million people visit SeaWorld parks each year. And they hope each -- leaves with a greater understanding of these remarkable animals and the challenges they face in an increasingly imperiled marine environment even -- -- says she doesn't want a CC world closed down. Just change. I think that they have the financial resources to be able to sort of shift this -- marine park circus like environment. Into one of education with summer's arrival thousands of visitors will be coming to SeaWorld in Orlando thrilled at the site of to a -- performing in captivity. As he has for the past 21 years. For Nightline -- Lindsey Davis in New York. Black fish is running as part of the American Film Institute verified -- film festival in Washington DC. That festival celebrating excellence in documentary filmmaking and storytelling. With a range of documentary showings in discussions through the weekend. And black -- opens in select theaters in new York and LA on July 19 and thanks to Lindsay from -- asked that.
This transcript has been automatically generated and may not be 100% accurate.