There's a Killer among us!

The bad ass below has been wiping out my entire tank.
It's not like he's new to the group, he has been in their for over a year and all of a sudden he went psycho!! He was pretty low in the pecking order, but he waited it out an dmade his move. Over the course of two weeks he has wiped out all but one other cichlid and a sucker fish. He lives in a "ruins" thing where he has dug out all of the gravel and now darts his head in and out like an eel, just waiting for his prey to go by.  Vicious little SOB.