So sorry about your loss. Please do not blame the hawk for acting like a hawk. As advised, the safest place for your birds until if and or when the hawk moves on is safe inside a covered coop/run.
We have a serious hawk/owl/eagle problem where we live. It is not unusual to have them either flying over our run or roosting in a nearby tree just watching the birds. Luckily we have our run netted and watching is all they can do. Hawks have the law on their side. So as much as we would like to free range our birds, it is out of the question if we want to keep them safe and sound. You might have to face the fact that you are not going to be able to free range your birds either. Our hawks do not move on. They breed and nest in our timber. As long as you have a food source for the birds besides chicken, namely, rabbit, squirrel, snakes and rodents, you will have hawks around. Many of our hawks winter over in the area and are now fighting for territory with other hawks.
You didn't say if you have a rooster or two in your flock. Best protection for your girls that money can buy.
Please do not kill a bird of prey. You are only opening up a world of hurt for yourself with the law if you do. Cover your run, keep your birds safe and if the problem persists, call your local conservation dept and ask them for help. They do not want wild life to become nuisance problems for anyone.