Dawn Brancheau, who had 16 years of experience working with orcas, or killer whales, was apparently interacting with a male orca named Tilikum in knee-deep water when the animal grabbed her by her ponytail, and pulled her underwater, the Orange County sheriff's office said.

"Rescuers were not able to immediately jump in and render assistance to Brancheau due to the whale's aggressive nature," the sheriff's office said in a statement. "She was recovered from the whale by SeaWorld staff members after the animal was coaxed into a smaller pool and lifted out of the water by a large scale/platform that lay on the bottom of the smaller tank."

Investigators said all evidence and witness accounts indicate that the death was an accident.

Emergency crews responding to the scene initially believed that the victim had slipped or fallen into the orca's pool. But witness statements and a review by homicide investigators determined that the animal had pulled Brancheau into the pool, sheriff's officials said.

The 911 recordings relating to the incident have not been reviewed by investigators and are not available for release, investigators said.

Procedures to change
SeaWorld Orlando reopened on Thursday though Shamu Stadium, where the killer whales perform, was still closed.

The killer whale show at San Diego's SeaWorld was also suspended indefinitely, spokesman David Koonts said.

Trainers will continue to interact with Tilikum, but procedures for working with him will change, SeaWorld said.

Tilikum had been involved in two previous deaths. A SeaWorld spokesman said Tilikum was one of three orcas blamed for killing a trainer in 1991 after the woman lost her balance and fell in the pool at Sealand of the Pacific near Victoria, British Columbia. Tilikum was also involved in a 1999 death, when the body of a man who had sneaked by SeaWorld security was found draped over him. The man either jumped, fell or was pulled into the frigid water and died of hypothermia, though he was also bruised and scratched by Tilikum.

SeaWorld said on its blog Thursday that it is still reviewing Wednesday's incident.

"Many people are asking about the future care of Tilikum, the whale involved in the incident," the blog post said. "We have every intention of continuing to interact with this animal, though the procedures for working with him will change."

Brancheau, 40, was rubbing Tilikum from a poolside platform when the 12,000-pound creature reached up, grabbed her hair in its mouth and dragged her underwater, witnesses said. Trainers rushed to help but could not save her.

Workers tried to help her with nets as an alarm sounded, but it was too late.

'A little bit stunned'
Brancheau's interaction with the whale appeared leisurely and informal at first to audience member Eldon Skaggs. But then, the whale "pulled her under and started swimming around with her," Skaggs told The Associated Press.

Some workers hustled the audience out of the stadium while the others tried to save Brancheau.

Skaggs said he heard that during an earlier show the whale was not responding to directions. Others who attended the earlier show said the whale was behaving like an ornery child.

Skaggs left with his wife and didn't find out until later that the trainer had died. The retired couple from Michigan had been among some stragglers who stayed to watch the animals and trainers when the accident occurred.

"We were just a little bit stunned," said Skaggs' wife, Sue Nichols, 67.

Orcas regularly involved in deaths of trainers

'Grabbed the trainer by the waist'
Another audience member, Victoria Biniak, told WKMG-TV the whale "took off really fast in the tank, and then he came back, shot up in the air, grabbed the trainer by the waist and started thrashing around, and one of her shoes flew off."

Two other witnesses told the Orlando Sentinel that the whale grabbed the woman by the upper arm and tossed her around in its mouth while swimming rapidly around the tank. Brazilian tourist Joao Lucio DeCosta Sobrinho and his girlfriend were at an underwater viewing area when they suddenly saw a whale with a person in its mouth.

The couple said they watched the whale show at the park two days earlier and came back to take pictures. But on Wednesday the whales appeared agitated.

"It was terrible. It's very difficult to see the image," Sobrinho said.

NBCs' Orlando affiliate WESH reported Thursday that the attack was captured on a home video. Another home video reportedly shows the whale and trainer, but does not show the actual incident.

Previous kills
Because of his size and the previous deaths, trainers were not supposed to get into the water with Tilikum, and only about a dozen of the park's 29 trainers worked with him. Brancheau had more experience with the 30-year-old whale than most. She was one of the park's most experienced trainers overall.

"We recognized he was different," said Chuck Tompkins, head of animal training at all SeaWorld parks. He said no decision has been made yet about what will happen to Tilikum, such as transferring him to another facility.

Job dangers
Brancheau's older sister, Diane Gross, said the trainer wouldn't want anything done to the whale because she loved the animals like children. The trainer was married and didn't have children.

"She loved the whales like her children, she loved all of them," said Gross, of Schererville, Ind. "They all had personalities, good days and bad days."

Gross said the family viewed her sister's death as an unfortunate accident, adding: "It just hasn't sunk in yet."

Dawn was the youngest of six children who grew up near Cedar Lake, Indiana. Her passion for marine life began at the age of nine, Gross said, on a family trip to SeaWorld.

According to a profile of Brancheau in the Sentinel in 2006, she was one of SeaWorld Orlando's leading trainers. Brancheau worked her way into a leadership role at Shamu Stadium during her career with SeaWorld, starting at the Sea Lion & Otter Stadium before spending 10 years working with killer whales, the newspaper said.

She also addressed the dangers of the job.

"You can't put yourself in the water unless you trust them and they trust you," Brancheau said.