Why a man eats another man's heart

This is from a video that is circulating on the Internet. The appalling footage has all the world asking: What kind of people could do this?

We tell ourselves these men must be monsters, people utterly unlike us, people we could never understand. But we don't say this because it is true. We say this because it is comforting to think so. The far more frightening possibility we must face is that such evil is not diabolically inhuman or beyond understanding.