Updated at 3:38 p.m.
Officials say trainers had to coax an aggressive whale into a smaller pool and use a platform to lift it out of the water before they could free a colleague from its jaws.
The Orange County Medical Examiner says 40-year-old trainer Dawn Brancheau probably died from multiple traumatic injuries and drowning after the killer whale Tilikum pulled her into a pool at SeaWorld Orlando on Wednesday.
The county sheriff's office says co-workers couldn't immediately help her because the whale was so aggressive after it.
The office says an investigation is continuing but there are no signs of foul play and all evidence indicates it was a tragic accident.
The new details became public as federal documents are providing more details about how the whale got to the U.S. Documents show SeaWorld asked federal marine officials for permission to temporarily house Tilikum in Orlando after killing a trainer in 1991 because the whale needed medical care he couldn't get in Canada.
That trainer died after she lost her balance and fell in the pool at a park near Victoria, British Columbia.
National Marine Fisheries Service official Nancy Foster said in a letter then that neither the Canadian park nor SeaWorld took precautionary steps necessary for Tilikum's health and welfare.
In yesterday's incident, the whale apparently grabbed Brancheau by her long ponytail, according to SeaWorld's head trainer Chuck Tompkins. Tompkins told ABC's "Good Morning America" that her ponytail swung out in front of the whale.
"That's when the trainer next to him (Tilikum) said that he grabbed the hair, pulled her under water. And of course, held her under water," Tompkins said.
Horrified visitors who had stuck around after a noontime show watched Tilikum charge through the pool with Brancheau in his jaws.
"We like to think we know 99.9 percent of the time what an animal is doing," he told The Associated Press on Thursday. "But this is one of those times we just don't know."
Tompkins told the Orlando Sentinel that he expects SeaWorld to keep the orca. If Tilikum were released into the wild, Tompkins doubted the whale would survive.
"I think it's unfair to do that to an animal," Tompkins told the newspaper.
Tompkins said the whale won't be isolated from other killer whales at the Orlando park.
Tompkins said Thursday that the whale plays an important role in the social group of eight whales who live at Shamu Stadium. He's the father of some whales and will continue to mate with other females.
SeaWorld says trainers will continue to interact with Tilikum but the procedures for doing so will change in the wake of trainer Dawn Brancheau's death.
The killer whale shows are on hold for now and Tompkins says they won't start again until trainers understand what happened to her.
At the same time, SeaWorld in San Diego is suspending its Shamu whale show for a second day. Spokesman David Koontz says SeaWorld is offering its trainers counseling and reviewing its procedures, including how trainers interact with animals. He says officials don't know when the show will resume.
Tompkins says the Orlando park will change safety protocols as needed but he doesn't expect drastic changes.
Tilikumby the staff at SeaWorld Orlando.
According to the Sentinel, trainers were forbidden with swimming with Tillikum, a 12,000-pound orca nicknamed "Tilly."
Brancheau was one of less than half of the park's 28 trainers who were allowed to work with the whale.
Brancheau was rubbing the whale from a platform when he grabbed her ponytail in his mouth and took her underwater.
Visitors who stayed after an afternoon show
Reports that Tilikum had been acting strangely leading up to Wednesday's tragedy were dismissed by Tompkins.
Tompkins said the whale had been very cooperative and at the time he dragged Brancheau into the water, she was rewarding him for how well he had performed that day.
"There wasn't anything to indicate to us that there was a problem," Tompkins told CBS' "The Early Show" Thursday.
He added: "We were very careful with how we worked with him."Tilikum had a marked history, however. The whale, along with two female killer whales drowned Keltie Byrne, a trainer, in 1991 at a British Columbia park and in 1999, Tilikum killed a man who had sneaked into the SeaWorld tank after hours to swim with whales.
Russ Rector, an animal-rights activist, tells the Sentinel that Tilikum did not belong at a theme park.
"Tilikum is a killer," Rector told the paper. "If this had been a dog that killed Keltie Byrne, it would have been put down."