I think you missed the point of him having a sidearm. In some places they are needed to get you out of trouble as opposed to being used for hunting or getting food. So they are often only used when someone is in trouble, like stepping on a big rattler that is longer than you are. That would have been a moment of danger for those involved, so it's no surprise that it ended like it did. Same thing happens a lot in Africa when you go on safari; the guides dont walk round with rifles but you can be sure one would appear pretty quickly if it was needed, when a customer's life was in danger. Having a gun does not always mean someone is actively out hunting; a point that may be lost on some. So in many of the wilder places on this planet having a firearm is not about getting dinner, it is often about having something that can stop you becoming a predator's dinner...
I think the people in the story had a serious brown trouser moment when 6 feet of hissing rattle snake appeared in front of them & given what I said above, the result is not unexpected. That is just the way it is in some places.
I think most people are assuming he was hunting because the article states they were at their hunting lodge. However you're right, they weren't actively hunting at the time. It says they were working the food plot. Food plots at a hunting lease are not there for human consumption but are there for the off season benefit of the wildlife and as a means of predicting the in season game trails.