"I don't think there's ever been a report of a killer whale attacking a human," said Wayne Perryman, a marine biologist at the National Oceanic and Atmospheric Administration (NOAA), who has studied killer whales in the wild.
Perryman knows of a report of a killer whale coming up from the ice in Antarctica and bumping photographers, but in that case, the animal "slid back in the water and swam away," he said.
"Shamu" Kills Trainer
Dawn Brancheau, an experienced 40-year-old animal trainer at SeaWorld Orlando, was killed yesterday afternoon. Billed as Shamu, Tilikum, a 12,000-pound (5,440-kilogram) male killer whale, reportedly grabbed Brancheau by the upper arm and pulled the trainer underwater.
Witnesses attending a "Dine with Shamu" show at the time of the trainer's killing report that Tilikum thrashed Brancheau around while swimming rapidly around SeaWorld's Shamu Stadium pool.
Killer whales are known to shake large prey to break them apart, but Perryman doesn't think that's what happened to the SeaWorld trainer.
"I don't think the animal was trying to eat her. It just roughed her up," he said.
Perryman points out that other captive animals are known to snap and turn on their trainers—not just killer whales.
"I think this isn't really a killer whale issue," he said. "It's when you're dealing with large mammals in a captive situation.
"It doesn't make a difference whether its elephants or bears or whatever. These kinds of things can happen."
"Shamu" Naturally More Aggressive?
Like humans, some killer whales may be more naturally aggressive than others.
"Animals that are used to living in social systems like killer whales vary—they're not all identical," Perryman said. "And the other thing is, they have good days and bad days, just like we do."
Tilikum has been involved in two deaths before.
In 1991, Tilikum and two other killer whales drowned a trainer at Sealand of the Pacific in British Columbia, which shut down soon after.
In 1999 a dead man was found lying across his back at SeaWorld Orlando. In the latter case, authorities concluded the man had snuck into the park after hours and likely drowned after suffering hypothermia.