My bet, I have 500 on the Oscar. LOL!
I have Plecos in my community tank, in with my guppy fry, and in with my South American cichlids (12 highly aggressive South American "cichlids", 2Plecos, 1 ordinary crayfish, and 1 blue lobster). They're doing great up to now, but I had 2 ordinary crayfish, until one of them got eaten by the "cichlids." That's why I think the Oscar did it.