The one being eaten was probably dead allready. Fish (and invertabrae) are sometimes canabilistic.

"Ghost Shrimps do not eat the deads of their own kinds."

I am sorry, but that is complete drivel.

Shrimps are scavengers and will eat anything that won't fight back.

I've never actually seen a ghost shrimp eat a dead ghost shrimp myself, but they devour each other's molted skin quite readily. And anything else that's dead, for that matter. I agree that the one was probably already dead. Or perhaps you only saw it eating a molted skin? The remaining skin looks pretty much identical to the live shrimp. I thought one of my Amano shrimp had died the first time I saw molted skin.

I'm not sure there's any such thing as an evil ghost shrimp. I've seen them poke at each other, looking for all the world like those crabs in Finding Nemo, but they're very peaceful.

I want to know the reason as well.. I recnetly bought 8 ghost shrimp the biggest ones started to pick off all the little shrimps. I saw my shrimp eating each other alive or dead they eat it till there is nothing left. I have one left.

Have you been feeding the shrimps? If not, that's probably the answer: they are hungry, so hungry that they turn into cannibals. The fish shops I go to hardy feed the shrimps because they usually are cheap and abundant. Feed them sinking wafers, they do enjoy this in my experience.