Maybe you could cover you coop and keep the chicken in there for a couple of weeks.
Once the hawk realises it can not get anything to eat it should go off some where else to find food.
Shooting at it will also frighten it off. Same as any sudden loud noises. If you do it enough it will learn to avoid you coop.
I am not sure you should shoot it with a pellet gun, because that might injure it and not kill it. Then it will die a slow lingering death as it can't hunt.
If you can shoot it, its best to shoot to kill.
Once the hawk realises it can not get anything to eat it should go off some where else to find food.
Shooting at it will also frighten it off. Same as any sudden loud noises. If you do it enough it will learn to avoid you coop.
I am not sure you should shoot it with a pellet gun, because that might injure it and not kill it. Then it will die a slow lingering death as it can't hunt.
If you can shoot it, its best to shoot to kill.