Just yesterday, I was watching a pack of Komodo Dragons ... well, eat the corpse of some mammal. It was a video - I didn't see it in real life. But the point is: they weren't eating each other.
Well the adults are cannnibalistic, known to eat the young ones.
As far as I know ALL carnivorous snakes and lizards are potentially cannabalistic, that's why herpetologists have to be extremely careful not to keep different sized snakes or lizards together.