Coopers hawks are grey when mature. check this picture link
https://www.bing.com/images/search?view=detailV2&ccid=C1fK5ypL&id=BA866DD3578F19954472852134A8F943F2E723F6&thid=OIP.C1fK5ypL_9Uk4gLrWSZ4kwEsDw&mediaurl=http://cdn.audubon.org/cdn/farfuture/LmLmrM2FLss4zLn5qKcjILFaZmDKByXfYqobSFhKF0U/mtime:1422549373/sites/default/files/Cooper%2527s_Hawk_l07-53-038_l.jpg&exph=820&expw=1024&q=cooper's+hawk&simid=607986673147710079&selectedIndex=3&ajaxhist=0
They will kill an adult chicken too but they are absolutely murder on young ones who should be kept in if you don't want to feed the hawks. They will come back if you leave the carcass out. The mate will also visit the kill. Coopers hawks are the most common of the hawks that kill chickens. Sometimes they are also barred brown and white when young. Females are larger than males. They are very good flyers.
https://www.bing.com/images/search?view=detailV2&ccid=C1fK5ypL&id=BA866DD3578F19954472852134A8F943F2E723F6&thid=OIP.C1fK5ypL_9Uk4gLrWSZ4kwEsDw&mediaurl=http://cdn.audubon.org/cdn/farfuture/LmLmrM2FLss4zLn5qKcjILFaZmDKByXfYqobSFhKF0U/mtime:1422549373/sites/default/files/Cooper%2527s_Hawk_l07-53-038_l.jpg&exph=820&expw=1024&q=cooper's+hawk&simid=607986673147710079&selectedIndex=3&ajaxhist=0
They will kill an adult chicken too but they are absolutely murder on young ones who should be kept in if you don't want to feed the hawks. They will come back if you leave the carcass out. The mate will also visit the kill. Coopers hawks are the most common of the hawks that kill chickens. Sometimes they are also barred brown and white when young. Females are larger than males. They are very good flyers.