A day after a whale at SeaWorld Orlando killed its trainer during a public show at the park's Shamu Stadium, a marine biologist with the Monterey Bay Whale Watch said the animal may had not do it intentionally.

The 12,300-pound orca dragged the trainer woman under the water and trashed her around violently on Wednesday, according to an audience member interviewed by WKMG.

I just think the killer whale may have wanted a social companion and just held her under too long, marine biologist Nancy Black told LiveScience. I would think the killer whale didn't do it intentionally but more as a play thing. They're so powerful.
But other reports contradict this opinion.

The orca which name is Tilikum, has always been regarded as an especially dangerous whale by the staff at SeaWorld Orlando and trainers were forbidden with swimming with it, the Orlando Sentinel reported.

This is not the first fatal incident with the Orca. The animal reportedly killed Daniel Dukes in 1999, a homeless man who accessed the tank in after-opening-hours, and it was involved in an incident resulting in a trainer's drowning in 1991, CBS News reported.