SeaWorld trainer's recorded final moments before being dragged into water by orca

Video shows the moment a trainer at SeaWorld was seized by an orca and dragged to her death.

The trainer was Dawn Brancheau, who had worked at SeaWorld for some 16 years, including with bull orca Tilikum who was the subject of 2013 Netflix documentary Blackfish.

Tilikum was a large orca who had been captured when he was just two years old.

The enormous whale weighed around 12,500lbs, and had fathered multiple calves at SeaWorld.

At the time of his attack on Dawn he had already been involved in the deaths of two other people.

The first was Keltie Lee Byrne, 20, who was killed at Sealand off the Pacific in 1991 after slipping and falling into a tank containing three orcas, including Tilikum.

In 1999 27-year-old Daniel P. Dukes became the second death attributed to Tilikum.

Daniel had stayed in the park after it closed, and his body was found in the whale enclosure having been mutilated by Tilikum.

After Daniel's death Tilikum was ruled to be too dangerous to swim with, even for trainers.

Tilikum the orca, with the floppy dorsal fin characteristic of captive orcas (Gerardo Mora/Getty Images)

In 2010 Dawn had been working with Tilikum from the side of the pool when some of her hair had floated into the water.

In a police report Jan Topoleski told investigators: "Dawn was lying on her stomach... Tilikum was interacting with her nose to nose. Dawn's long hair floated on the water in to Tilikum's mouth."

Topoleski recalled how Dawn had begun struggling to free her hair from Tilikum's mouth, which had prompted him to push the alarm button.

When he turned back after hitting the alarm Dawn had disappeared.

CCTV from the park shows Dawn entering the water at 13:38.

Five horrible minutes later at 13:43 and Tilikum could be seen swimming around with her lifeless body in his jaws.

Her body could not be retrieved from the pool for 20 minutes.

Below the water's surface visitors and staff witnessed Dawn's final moments as the orca dragged her around the tank.

Tilikum was involved in the deaths of three people (Gerardo Mora/Getty Images)

Staffer Lynne Schaber had been waiting for the signal for Tilikum to descend so visitors could get photos.

Instead she witnessed Tilikum killing Dawn in the pool, saying that he never let her go up for air despite her frantic efforts to surface and breathe.

One witness claimed that as they saw Dawn trying to get out of the water they saw Tilikum 'impact her squarely in the chest'.

They added that he had 'looped around and came back towards Dawn Brancheau with his mouth open.'

Even after Dawn's body had been recovered witnesses reported that Tilikum had tried to retrieve it.

The precise reason for Tilikum's attack has never been established.

Orcas rely on sonar to communicate, and one theory has suggested that the concrete tanks in which they are held echo their own voice back at them as it bounces off the walls.

It has been noted that no fatal attacks on humans by wild orcas have ever been recorded, only by captive orcas.