Visitors to SeaWorld in Orlando, Fla., watched in horror as a killer whale grabbed its trainer by the arm, dragged her underwater, and turned her over and over until she drowned.
Trainer Dawn Brancheau, 40, had just finished the noon show with Tilikum, a five-ton orca, known as killer whales. Brancheau was rubbing him when he grabbed her by the upper arm and pulled her in the water.
The whale, nicknamed Tilly, has been involved in two previous incidents.
During a performance in 1991 at Sealand in British Columbia, Canada, he and three other orcas were blamed for the drowning death of a trainer.
In a second incident in 1999, park officials found the body of a naked man lying on Tilly's back. Authorities concluded that the man had drowned after suffering hypothermia in the 55-degree water and afterward, the whale played with his body as with a toy, tearing off his swim shorts.
Because of this history, Tilly is kept away from other orcas at the park and trainers do not get in the water with him.
At a press conference on Wednesday, SeaWorld Orlando General Manager Dan Brown described Brancheau as "one of our most experienced animal trainers."
"This is an extraordinarily difficult time for SeaWorld parks and our team members. Nothing is more important than the safety of our employees, guests and the animals entrusted to our care," Brown said.
"We extend our deepest sympathies to the family and friends of the trainer and will do everything possible to assist them in this difficult time," he said.
Brancheau, who had worked at SeaWorld since 1994, began her career training sea lions and otters and had been working with killer whales for the past 10 years.
Wednesday's death was the second time in two months that a trainer was killed by an orca. On December 24, Alexis Martinez Hernandez, 24, died while practicing a routine with Keto, a 14-year-old orca, at Loro Parque on the Spanish island of Tenerife.
When Hernandez fell from the whale's back, he was accidentally crushed to death .
AP contributed to this report.