Hi, please help. We came home this afternoon to find one hen killed and another critically injured. Both were attacked on their backends and were a bloody mess. The third Columbian was bitten on the back of the head but we think she'll make it. Not sure what could have gotten to them. They are housed in a coop during the night and we let them out in the morning into a covered dog kennel (covered and surrounded by chicken wire). The hens were found in the coop. I can't remember if I saw them with the rest of the chickens when I let them out this morning. We are new to chickens. Was it a coincidence it was all our CWs? We have anconas, astrolorps, leghorns and new hampshire reds. Also, guineas. They are all very calm and we have never seen them go after each other.