Nobody expected Dawn Brancheau - one of SeaWorld's most experienced trainers - to be mauled to death by the killer whale she'd trained and loved.

Witnesses at the Dine with Shamu show could only look on in horror as Tilikum, the largest bull orca in captivity, took her long ponytail in his mouth and dragged her into the pool during a petting session in February 2010.

She tried to pull it free but at 126lbs, Dawn, 40, was no match for the 12,500lb, 22ft-long whale, who only yanked harder.

Her colleagues immediately initiated their emergency procedures, slapping the water in a signal to Tilikum to stop and dropping a weighted net to try and separate the whale from the woman.

But he refused to respond. At one point Dawn managed to break free and swim to the surface but Tilikum slammed into her, clamped his jaws around her middle and shook her violently.

Spectator Victoria Biniak told WKMG-TV how the animal, took off really fast in the tank and he came back, shot up in the air, grabbed the trainer by the waist and started thrashing her around, and one of her shoes flew off.

He was thrashing her around pretty good - it was violent."

Even when staff managed to guide him to the medical lift and raise the floor he refused to let Dawn go. Trainers were forced to pry his jaws open and pull their colleague free as her arm came off in his mouth.

She had been scalped and dismembered and had almost every bone in her body broken before being drowned.

And despite SeaWorld putting the incident down to 'trainer error', several former trainers claimed they believed Tilikum knew exactly what he was doing.

"He got her down and that was it - she wasn't getting out," former trainer Jonathan Smith told Outside magazine.

"I truly believe that they are smart enough to detect and know what they are doing. He's going to know she is trying to get to the surface."

Former trainer Jeffrey Ventre agreed. "If they let you out, it's because they decide to," he added.

"We don't know for sure what motivated Tilikum. But there's no doubt that he knew exactly what he was doing. He killed her."

But what many didn't know is that Tilikum had killed before.

He'd been involved in the 1991 death of a 20-year-old trainer at Sealand in Victoria, Canada before being sold to SeaWorld.

And in 1999 Daniel Dukes, 27, was found splayed naked on Tilikum's back covered in bite marks and puncture wounds.

Out of four known fatalities involving killer whales in captivity, Tilikum had been involved in three.

Experts told 2013 documentary Blackfish they believed his capture and captivity had rendered the intelligent, sensitive animal 'psychotic' - claims SeaWorld has denied.

He was just two years old when he was torn away from his family off the coast of Iceland and taken to a concrete holding tank at Hafnarfjrdur Marine Zoo near Reykjavk.

There, he reportedly spent close to a year either swimming in circles or floating still on the surface before being shipped to the rundown Sealand of the Pacific, a marine park just outside Victoria, on British Columbia's Vancouver Island in 1984.

The documentary heard how he was housed with two older female orcas named Haida II and Nootka IV who sought dominance, with females being at the top of the social structure in the wild.

For 14 hours a day, the incompatible trio were allegedly forced into a 26ft wide enclosed mental-sided pool known as the module where the females raked Tilikum with their teeth in the darkness.

He is said to have started suffering from stomach ulcers and was eventually isolated in a medical pool to protect him from the bloody attacks.

And on February 20, 1991, the trio killed University of Victoria marine biology student and part-time trainer Keltie Byrne, 20, when she slipped and fell into the orca pool after a show.

According to witnesses, one whale grabbed her in its mouth and dragged her around the pool underwater.

Horrified witnesses described how the champion swimmer screamed, "I don't want to die," as she fought to escape and reach the side. But every time she managed to break free, the orcas pulled her back.

"I just heard her scream my name," trainer Karen McGee recalled.

"I threw the life-ring out to her. She was trying to grab the ring, but the whale, basically, wouldn't let her. To them it was a play session, and she was in the water."

They tried to distract the trio by throwing fish and banging buckets but none of their usual commands worked. Keltie is said to have come up screaming one last time before she finally drowned.

It took employees two hours to get the orcas to release the Keltie's body, which the whales had stripped and covered in bruises from bite marks.

Al Bolz, Sealand's manager, told reporters at the time, "It was just a tragic accident. I just can't explain it."

But Paul Spong, director of OrcaLab, in British Columbia who had done research at Sealand, saw it a different way.

"If you pen killer whales in a small steel tank, you are imposing an extreme level of sensory deprivation on them," he said.

"Humans who are subjected to those same conditions become mentally disturbed."

The park closed soon after and Tilikum was sold to SeaWorld Orlando where he sired 21 calves, making him the industry's most prolific breeder.

There, trainers told the documentary they were unaware of his past, but on the morning of July 6, 1999, SeaWorld physical trainer Michael Dougherty glanced in the underwater viewing area by his office and saw Tilikum looking back with two human feet hanging down his side.

The victim was Daniel Dukes, 27, who had attended the park the day before and evaded security to stay overnight, seemingly to take a moonlight swim with Tilikum.

His clothes were found in a neat pile by the side of the pool and an autopsy discovered he'd suffered cuts and puncture wounds to his head, body and left leg with his testicles ripped open.

Without camera footage or witnesses, the coroner recorded a verdict of death by drowning and hypothermia.

Then came Dawn's killing.

A SeaWorld spokesman has denied that Tilikums killing of three people showed aggressive intent and in January 2017 he died from a bacterial infection aged 35.

See more here:

SeaWorld trainer torn limb from limb by killer whale turned 'psychotic' by captivity - Mirror Online