Killers of the Fourth Kind

To scientists among your kind, there are three types of Killer Whales; the first are a noisy and sociable group who eat only fish and inhabit fixed territories within coastal waters. You call them Resident Orcas. The second type is far more reclusive and taciturn. They are nomads of littoral seas who eat only mammals, including other dolphins and whales. You know them as Transient Orcas, and these cannibals are pariahs among my kind. Much is known among your scientists about both these types. However, that is not the case with the third type of Orca, for they are a breed apart. They live far out in deep, bluewater and never interbreed with the other two types. Although they eat mammals, their preferred prey are sharks. You refer to them as Offshore Orcas, and they are a fierce and powerful breed best left alone by both your kind and mine.
Having said this, there is another kind of Orca, whom I shall call Killers of the Fourth Kind. These Orcas were captured in the wild and doomed to spend foreshortened lives of mindless boredom and emotional anguish in your aquariums and sea parks; or they were born in those confined concrete tanks and will never know the joy of freedom. Either way, they are the equivalent of those whom you keep on death row, and like them, these Killers of the Fourth Kind have nothing to lose by venting their rage in the worst way possible. They have killed humans before and they will do so again. Count on it.