If the shooting is considered reckless, that it is against Indiana law, but based on your story, I would talk to the State Police. I do not understand you not filing charges concerning the assault.
I'm completely at a loss here. There are wolves, there are sheep and there are sheep dogs. If a wolf breaks my finger, I savage the wolf and I do it swiftly, surely and severely. I echo your understanding of every State I know of regarding reckless discharge of a firearm. You cannot allow a bullet to just be "at large" and not know your backstop.
If a deer comes down and dies at your pond this would have nothing to do with a backstop and there is no crime, it is simply how the cookie crumbles. A hunter cannot control where an animal will die anymore then we can control the next time we need to urinate. If an animal is shot and dies on my property the protocol, by law, is to have the hunter ask me to be able to come and fetch it which I kindly do. I also do not require anyone to even ask me to come and fetch it, my neighbors all know that they have carte blanche permission to gather up any kill from my land, ride their horses over here, let the kids play, whatever so long as they don't destroy anything. They allow me the same courtesy.
