So sorry. You will need to fortify that right away or the predator will be back to take out the rest. If the attack happened at night, a raccoon or fox seems likely. Raccoons are incredibly strong and persistent. Is the coop securely locked at night? A 2-step locking mechanism is required to...
So sorry for your losses. The wounds need to be cleaned and perhaps antibiotic ointment without painkiller applied.
You also need to determine what caused this. How is mama duck? This seems like a predator attack to me. What predators do you have where you live and what is your set up like?