I came home this evening to lock up the coop for the night and 15 of my 16 chickens were dead. The rooster was missing some feathers and 2 hens had a couple of scratches and a little blood on their necks. All the others are completely unmarked. The hen still alive can't stand up and is in shock I think.. I've had them for years without any problems. It happened in daylight because they hadn't come inside, they are all scattered over their yard which is about 1000 square feet. Has anyone any idea about what could have happened?