Whether it's because of a friend, an ex, or a family member, we've all felt the familiar sting of jealousy. "Thou shalt not covet" might be a good rule and all, but jealousy is a human emotion that's often hard to turn on and off. The following people held so little control over their feelings of jealousy that they ended up killing because of them. In many cases, the jealousy started out small and grew bigger and bigger to eventually take over their every thought and action. These criminals remind us that allowing jealousy to consume you can end in horrific tragedy.