I have not heard anything about this terrible tragedy but my sympathy goes out to everyone involved in any way.
Since I was not there and don't know anything of the circumstances involved, I'd hate to make a judgment about blame but it sounds like a problem of supervision and has been pointed out, common sense.
We should always be certain that any shooter is able to handle any gun and usually, that involves limiting the number of cartridges that are available to fire. That's one reason that many "starter" guns are single shots.
Whenever I've introduced a shooter to a semi-automatic or self-loading firearm, I've first loaded it with only 1 shell, just to be certain that there's a real understanding of how it functions. I'll then load it with 2 shells and make sure that I'm standing very close to keep the muzzle downrange, just in case.
You are of course correct that folks who are anti-gun will seize upon this as an indictment of all shooters and gun owners. People make mistakes in all areas of life and unfortunately, some of those mistakes are tragic and sometimes fatal. We as responsible gun owners should do all that we can to emphasize safety and responsible use of firearms.
"If he's out of range, it just means that he has another day and so do you."