There are times of the year and in certain locations that there is very little you can do to protect your flock of chickens other than sit on your deck with a shotgun.  The other half of last year’s flock was killed today while in what we thought was a secure coop – closed in.  Cement foundation, wired windows, new door.  Once the carnage is cleaned up the forensics will begin, maybe.  Having to deal with your hens being killed by something two years in a row is too much really.  Makes you never want to raise a chicken again.