Let’s start with the movie’s central contention.  Killer whales can become hyper-aggressive when confined in captivity.  To make this case, the documentary focuses on Tilikum, a 32-year-old male orca. Tilikum was captured in the northern Atlantic Ocean in 1983 and taken to Sealand of the Pacific, a now-shuttered park near Victoria, British Columbia. Former Sealand trainers interviewed in “Blackfish” say the park’s female killer whales would aggressively gang up on Tilikum, particularly when they were confined in a 20-foot-by- 30-foot pool overnight. In February 1991, Tilikum and two other orcas attacked part-time trainer Keltie Byrne after she slipped into their pool. She died after being dragged and submerged under the water. Two witnesses interviewed in “Blackfish” claim Tilikum was the instigator of the incident though that wasn’t broadly established immediately after Byrne’s death.  SeaWorld later acquired Tilikum, and according to an ex-trainer who appears in the documentary, he was repeatedly attacked by female orcas who shared the same living space.  In July 1999, a SeaWorld Orlando employee found 27-year-old Daniel P. Dukes, who was believed to have wandered into the area after hours, dead in Tilikum’s pool. Dukes’ body was draped over Tilikum‘s back when the worker found him. An autopsy later determined Dukes drowned but noted dozens of bruises and cuts. “Blackfish” argues Tilikum may have attacked Dukes before and after his death.  The third and most-publicized Tilikum-related death came in February 2010. Tilikum dragged senior SeaWorld trainer Dawn Brancheau into the pool and forced her underwater, eventually killing her.  SeaWorld has since said Tilikum grasped Brancheau’s ponytail. The movie – and the U.S. Occupational Safety and Health Administration – argue Tilikum pulled on Brancheau’s arm. An autopsy later determined she died of drowning and traumatic injuries, and that part of her scalp was “forcibly torn from her head.”