I knew exactly what it was when you said the intestines were only ate. We had the exact same thing happen. Our Rhode Island Red chickens decided to eat our Plymouth Barred Rock chickens one day at the drop of a hat. It was crazy! We had three of each breed and they just flipped their lid one day and killed the others. I was ready to shoot them but my wife convinced me to give them away. We were upfront with the people taking them about what happened. Crazy huh?!?! Where we lived at the time, we called it cannibal hill.