On February the 20th 1991, the captive bull orca, Tilikum, drowned his trainer, Keltie Byrne at Sealand of the Pacific in British Columbia, Canada. It was the first recorded killing of a human by an orca whale. 19 years later - almost to the day - Tilikum killed another trainer, Dawn Brancheau. Rebecca Kesby has been speaking to Corinne Cowell, an eye witness to the first killing, and biologist Eric Walters, the whale trainer who warned the authorities 2 years before that keeping orcas in captivity could be fatal.

(PHOTO: SeaWorld orca Tilikum performs at SeaWorld Orlando in Florida, in 2009. REUTERS)