Help with a Predator!!!

[slabitabilo]

3 of my chickens were killed. They all 3 had broken necks but not blood and they had not been mauled. We have them in a coop and we have an 8' privacy fence around our 1 acre property. One of the chickens was dragged out of coop but left. What could have done this?

 

[Elkalite]

It might have been some kind of flying predator that could have caught them by the neck or head but didn't get a good grip, or the chickens were too heavy to fly away.