I would posit that a confident prosecutor would believe that the "I'm going to kill you!" statement takes 'accidental' off the table.
If Jay is not lying, the shooter's perspective would be irrelevant if I were the prosecutor in this particular case.
Three things, just because there was a threat doesn't mean the discharge was intentional. Second, there is NO proof that threat was ever made. There is the
claim that it was made, but unless backed up by Walker (and it apparently wasn't), there is no proof. There are no other witnesses or recordings of the event. You are down to he said/he said. Third, because of the he said/he said aspect, how do you know if Jay is lying or not. That is a HUGE 'if' about Jay lying, or anybody in a similar situation. How do you as the prosecutor determine of all aspects of Jay's story are true with no other witnesses? You have the GSW evidence, but that does not prove anything about intent. It certainly is not unheard of for a hunter to be unintentionally shot in the back.
So what are you going to take to the jury? Are you going with an unwinnable case that the defense will readily shoot down about how your client, "Honest Jay," never lies and never mispeaks and that the jury should only listen to what he says? Or are you going to take a winnable case that Jay was injured by the firearm of Walker?