Subtitles section Play video Print subtitles When a shark bites a human, they never get the same taste, let's say, as they would by biting a fish. So generally, they will release us and swim away. These incidents were totally different. The shark came in, attacked the victim, and came back and attacked again and again and again, and stayed with the victims until they were removed from the water. That's a very determined animal. NARRATOR: So what could cause sharks to display such brazen determination? For Collier, there can be only one explanation. In my opinion, these animals were not investigating. These were all predatory attacks. These sharks were attempting to feed on the victim. NARRATOR: Sharks trying to feed on humans. It's a terrifying and virtually unprecedented revelation. It's extremely unique and very, very rare. And we had to find out why. NARRATOR: So what could cause Egypt sharks to suddenly start attempting to actually eat beachgoers? For Dr. Dan Huber, such unnatural behavior suggests that something equally unnatural must be occurring in the predator's environment. In fact, it could point to some kind of human intervention. Animals can be trained to exhibit certain behaviors in response to a stimulus. And the reason why this works is because the stimulus is associated with a reward. NARRATOR: This concept is known as conditioning. One of the primary ways that this happens is if a shark gets hand fed over and over and over again, it's learning to associate people with a food reward. Which means that it's going to exhibit feeding behaviors around people, even if that food reward isn't present.