Sorry for your loss, free ranging is always a challenge.
If legal where you live, electric poultry netting is good against most land predators. Premier1supplies.com has it, and advice that's excellent also.
Keep your survivors locked in their safe coop and run until you can sort this out, at least. Annoyed but alive...
This was not a hawk, it's a four footed predator, who will be back. Can you set up a game camera? Might help ID this culprit.
Somehow it seems that the favorite birds are lost first, and it's hard to face. So sorry.
Mary