That's huge, just huge..... I came to this thread hoping to read something less devastating about a COOP being smashed or sumpin'. Not most of your beloved chickens!!! I am SO sorry.
Oh Kate this is just heart wrenching. I'm so so sorry. I know words just don't touch the pain and hurt you're going through. Wish I was there to help you get through it. Only us chicken people fully understand the pain.
Sounds like the first shots of a war. Whatever did it, get it (or them) right between the eyes!
I know what it is to lose an entire coop's worth - just 4 brand new chicks, though. Unfortunately, it was our dog that did it, so no .22 caliber solution.