June 21, 2013 -- SeaWorld trainer Dawn Brancheau and Tilikum, a killer whale, delighted an audience when they performed together, but the joyful scene of human and animal interaction ended when the giant orca pulled his trainer into the water and killed her.
Three years later, questions have persisted as to what led the 12,000-pound, 22-foot killer whale to behave in such a way, killing Brancheau, a woman who was remembered as one of the most gifted trainers at the Orlando, Fla., theme park.
"[I] didn't understand why a killer whale would essentially bite the hand that feeds it," said Gabriela Cowperthwaite, a filmmaker whose latest documentary, "Blackfish," examines how Tilikum and Brancheau arrived at that fateful moment three years ago and raises the question of whether killer whales should be held in captivity.
The American Film Institute's AFI Docs film festival in Washington, D.C. runs until Sunday.
"She's his trainer, so presumably they had this loving bond," Cowperthwaite said. "One of the things that shocked me the most was how violent and prolonged it was. That is the stuff of nightmares."
The violent death of Brancheau, a beautiful, blonde trainer who could have been the poster child for SeaWorld stunned the world, but judging by Tilikum's history, it may not have been a surprise.
There have been four deaths involving killer whales in captivity, and Tilikum, who makes a big splash with his audiences, has been associated with three of them.
John Hargrove, a former SeaWorld trainer, said the majesty and intelligence of the animals has made them into must-see attractions for visitors to the theme park.
"When people came to SeaWorld, they want to see that trainer in the water with those whales because they want their heart strings pulled on," he said. "They want to see the relationship between the whale and the trainer."
A 40-Year 'Experiment' Traced Back to the Beginning
In the wild, killer whales live in tightly-bound communities where the adult offspring never leave their mothers' sides.Each community has a completely different set of behaviors, including their own repertoire of vocalization.
The majestic animals also enjoy life spans similar to the length of a human life. The females can live to be more than a century old, while the males have a life span of 50 to 60 years.
"There is no documented case of a killer whale ever killing anybody in the wild. It's only in captivity where these incidents have happened," Cowperthwaite said.
In her film, she traces what she calls a 40-year experiment to capture the first killer whales for the first marine parks back to the beginning.
Speedboats, Bombs Used to Herd Whales
The first killer whales were taken into captivity four decades ago by teams in speedboats lobbing bombs into the water, according to Cowperthwaite's film.
The hunts separated young killer whales from their mothers, destroying their social connections, she said.
Tilikum was captured off the coast of Iceland in 1983 when he was about 2 years old.
"He is sort of taken from his mother at this very young age and then he's dumped in this park called Sealand of the Pacific and is beat up on consistently because ... he's always a subdominant male, he's always trying to figure out his place in the social order and the other two females there just kind of bully him consistently," Cowperthwaite said.
At night, Tilikum and the two other killer whales were kept in a holding pen just 20 feet across and 30 feet deep.
It was at Sealand of the Pacific in 1991 when Tilikum was responsible for the death of a trainer for the first time, grabbing her back foot and pulling her underwater.
Tilikum arrived at SeaWorld Orlando the next year to the delight of tourists who knew nothing about his killer past.
Eight years after his first kill, Tilikum may have been responsible for a second death in 1999 when a park visitor managed to stay after closing hours.
The circumstances leading to his death were unclear. However, the next morning the man was found draped across Tilikum's back, dead from hypothermia.
While fatalities have become a concern, the very behavior of a killer whale isn't 100 percent predictable.
From 1988 to 2009, SeaWorld generated 100 incident reports of killer whales engaging in undesirable behavior, including nearly a dozen that involved injuries to trainers.
In one incident captured on video, a trainer made the mistake of putting her foot on and off a killer whale. She clung to the gate but was ripped into the water.
"Your stomach drops because you know what's going to happen," said John Hargrove, a former SeaWorld trainer. "You hear her scream out, 'Somebody help me,' and the way she screamed it she knew she was going to die."
The trainer was eventually released but not before having her arm badly broken.
Dawn Brancheau tragically did not have a similar outcome, and in the wake of her death, the Occupational Safety and Health Administration undertook an investigation of the incident, resulting in SeaWorld being ordered to keep trainers behind barriers.
The requirement ended the intimate and dramatic acrobatic work that thrilled audiences, prompting SeaWorld to continue to appeal the decision.
SeaWorld said OSHA has a "fundamental misunderstanding of how to properly and safely care for and work around these animals."
Since Brancheau's death, the theme park said it has "voluntarily implemented significant changes to the training protocols for its killer whale program that have proven to be safe and effective."
SeaWorld said its marine park was an "invaluable educational resource" to the more than 11 million people who visit each year and said it hoped "each leaves with a greater understanding of these remarkable animals and the challenges they face in an increasingly imperiled marine environment."
With the summer tourist season kicking into full gear, thousands of visitors will be coming to SeaWorld Orlando, taking in the thrilling sight of Tilikum performing in captivity, as he has for the past 21 years.
Cowperthwaite wants SeaWorld to implement changes, not shut down its operations.
"There is a potentially very heroic role and very forward-thinking role for SeaWorld to take in all this," she said.
"I think they have the financial resources to be able to sort of shift this whole marine park, circus-like environment into one of education."