Its pretty much up to the Prosecutor of your area as to how you get treated after the fact. There are so many variables and even one single fact can change the outcome so much that this could be argued forever.
Using your scenario with no other facts changed.
You may be cuffed, you may not. Depends on the officer. The Sheriff or Police Chief or Designee will be called, he will arrive, what he decides will factor into how you are treated. He may take a statement right there. He may have you come to the station. He may take you to the station. You may go into the station in the back of a patrol car, in cuffs.
He may keep you overnight, he may not. He might release you and have someone else pick you up. He will advise you to contact an attorney. The Prosecuting attorney or even one of the local Judges may arrive and quiz you. They may decide to hold you, or they may let you go. If they let you go, you might not every hear from them again or they may decide to turn it over to a Grand Jury or you can even request one.
If its clearly a righteous shoot, it can be over pretty quickly. Often times the easy part is getting cleared by the law. Then the protracted nonsense from legal experts and the family's of the deceased come into play and try to mess up your life for years to come. Its a big hassle and can be very expensive. I heard it stated more than once that if the shooter knew what would happen after the fact that it would have been easier to get killed by the perp and be done with it.
Shooting is the easy part. When its over, your nightmares have only just begun...
This is small town America here where everyone knows everyones' business. In the big cities, you will probably be treated like a murderer until proven otherwise.
In actual practice, there is no correct answer. It is entirely dependent on the local practices and procedures.