Well, Homo Sapiens are KILLERs too. So are the "Flipper" type dolphins, who are closely related to the Orcas. They are carnivores, but they don't eat people. (Maybe people taste bad?) However they do eat the herbavoire whales, and seals and other mamamals in additon to fish. Seeing one go after a seal in the surf zone is impressive.
Point was, killer whales are killer whales. These things happen with carnivores of this size.