This is advice that can be offered if the rooster is still alive, after the deed, not so much.Instead of killing him, why not find him a new home or instead of keeping with other hens, put him with other roosters as a bachelor flock?
Personally, I agree with many others, ugly behavior is just that. There is nothing wrong with a good life and a quick end, we should all be so lucky.
I have seen the discombobulated reaction when there has been an upset - it has always passed in 2-3 days for me, and it seems like for you.
What one can miss, is not only is the hen being chased and harassed being traumatized, so are the other hens in the flock. Always solve for peace in the flock.
Mrs K