Two nights ago I had an attack and found 8 adult chickens dead. Checked again today and found 3 more dead. All were locked in a coop (found locked still) each time. The body was left untouched for the most part aside from the neck. One chicken seemed to have had its neck twisted though none of the heads were detached. All were killed in a similar manner with no parts eaten. What could this be? Of the 20 years, I have not seen anything like this has happen before which has left me feeling stumped as to what it could be. We have dealt with tree squirrels but that is all we tend to have around. If it helps, we are located in northern California. Animal? Rodent? Human?