A killer whale viciously attacked and killed a trainer at SeaWorld park in Florida on Wednesday, but a marine biologist says the whale probably did it because it was bored as killer whales don't normally kill humans in the wild.

They have never killed a human in the wild, said Nancy Black, a marine biologist with Monterey Bay Whale Watch, according to Live Science.

I just think the killer whale may have wanted a social companion and just held her under too long, Black told LiveScience.

Forty year old Sea World trainer, Dawn Brancheau, was killed on Wednesday after the killer whale named Tillikum, thrashed her viciously underwater as devastated eye witnesses looked on.

Black said the 12,000 pound killer whale was probably bored because of living in captivity for so long. Killer whales, or Orcas, are intelligent and social creatures and swim thousands of miles every day.

I would think the killer whale didn't do it intentionally but more as a play thing. They're so powerful.

Though it's the third time Tillikum has been involved in a human's death, there are reportedly no plans, by Sea World, to take the massive animal out of the show.

She added killer whales don't have to come up for air as often as a human might and could reasonably hold someone underwater for 15 to 20 minutes.

Another expert on wild Orcas', agrees with Black's understanding of what went wrong.

They are highly social animals, that tend to live in cohesive groups, so it's quite an artificial environment to capture them and put them in a small area, says Dr Andrew Foote from the University of Aberdeen, UK.

The tragic events are a reminder that orcas are wild, strong and often unpredictable animals, says Danny Groves, of the Whale and Dolphin Conservation Society.

More on Sea World's Killer Whale:

Dawn Brancheau's ponytail caused whale's attack: SeaWorld curator

Sea World committed to using whale after third killing

Shamu kills Sea World Trainer Dawn Brancheau