Well, guess what? Humans aren't the only killer ape! Scientists observing chimpanzees in the wild saw a group of them attack five adult gorillas plus an infant, driving off the adults while capturing, killing and eating the infant gorilla.
The New York Post has the story which was originally reported in the journal Nature. Inasmuch as our nearest modern relative among primates is the chimpanzee, apparently both we and the chimps inherited our omnivorous nature.