Since you like to deal in hypotheticals, let me propose one:
1) If the ranger were a private citizen demanding $14 owed to him, the camper became “beligerant and hostile”, the private citizen attemped a citizen’s arrest, the camper resisted, and the private citizen pulled out a gun and shot the guy, what do you think would happen?
2) If you answer “the private citizen would be prosectuted for murder”, then why should it be any different for the ranger?
The private citizen had no legal right to arrest someone for not repaying a $14 loan. But if the debtor became belligerent and hostile just from the request, giving the requestor reasonable grounds to fear physical harm, then a self-defense shooting is justified. What we just don’t really know here is whether the drunken camper’s actions provided grounds for a reasonable fear of physical harm on the part of the ranger. We also don’t know if the ranger deliberately shot the man in the back, or if the man was moving around unpredictably, and the ranger made the decision to fire when the man was facing him, and wasn’t able to stop when the man turned. I can only hope the jury heard all the available info and testimony, and made the right call.
If the ranger genuinely believed he was in danger of not making it home to his family if he didn’t shoot, I’m fine with his punishment being one year of electronic monitoring and ineligibility for future employment as an armed law enforcement officer. Since it seems to be agreed that the camper was not in fact armed, the ranger made an incorrect decision based on the belief that he was. However, there are many situations where a law enforcement officer is confronted with someone whose behavior is consistent with that of a violent criminal, sees the person reach into a pocket, and the person does in fact pull out a gun or knife. Sometimes waiting to see that it really is a weapon costs an innocent law enforcement officer his (or her) life, and costs the officer’s family a parent, spouse, adult child, etc. I don’t think it’s a good policy to give the benefit of the doubt to a drunken person who is refusing to pay a legally required fee to be in the place he’s in, over a ranger who was apparently just trying to do his job when the drunken non-paying person’s behavior turned in a direction that caused the officer to panic and fear for his life.