For every ND that kills someone, I'd bet there are a hundred that injure someone, or just leave a hole in the floor, or cause a TV set to blow up (Rule #1 violated by dry-firers who are surprised when there is a round in the chamber). One suspects a few family cats, ready targets for dry-firers watching TV in the barca-lounger, have died this way...
Every ND is an argument, in some minds, for more gun control. In addition to being a tragedy. This case (the woman shot by the child) is getting a lot of press coverage... being exploited on behalf of increased gun control.
I usually lose the argument about a round in the chamber in terms of numbers -- most people disagree with me, and that is probably the case on this forum, too. I will stand on one thing, though: my argument is not based on squeamishness or ignorance of guns. This is a moral argument, not a technical one.
The right to self-defense (and defense of innocents) has an unassailable moral and legal basis. As imperative as that is, it does not mean I can invoke "self-defense" without due diligence. The equation is NOT will I be better able to defend myself if I have a round in the chamber. If that were the only test, then there should always be a round in the chamber! What is my calculus? Is the reduction in threat to me with a round in the chamber, compared to risk with the first round still in the magazine, worth the increased threat to me and to others caused by the potential for a ND? I believe the answer is no, even if the risk is statistically very small, because of the moral responsibility involved if I hurt an innocent person by mistake.
(And note that this argument does not apply to the Police, who have an imperative to respond to violent actors, thus bringing great and unpredictable danger upon themselves AND the requirement to apply force to protect society, which justifies carrying rounds in the chamber).
I do not believe my right to defend myself outweighs everyone else's right to be safe. In the logical extension of this principle, I have drilled and drilled on the idea that I will not shoot unless a life is threatened, and I'm not shooting unless I am sure of where that bullet is going if it misses or passes through the person (or beast) threatening innocent lives. For most city/suburban scenarios, this rule means I do not intend to fire unless I know exactly what the backstop is going to be. I expect to run away, or hold fire and maneuver to a better firing location, yes potentially increasing the risk to me, to avoid hitting an innocent victim somewhere behind the threat.
Likewise, I practice a lot at the range, building on several shooting courses attended over the years, to increase the odds I will hit what I am going to shoot at. Which is part of the due diligence required before using a weapon in a defensive situation, in my opinion. Similarly, I select ammunition suited for the potential target and environment -- usually the Speer Gold Dot Short Barrel Ammunition 38 Special +P 135 Grain Jacketed Hollow Point for my J frames.
That's just my philosophy. If you think my premise is correct -- that our firearms can potentially hurt innocent life as well as protect it -- there is a lot to think about, and perhaps getting that first shot off quickly is not #1.
In short, I don't think this shooting was necessary nor is it morally justifiable under the doctrine of self defense. Mindset, training, good procedures, safe carry, layers of safety well thought out (including an empty chamber), positive control of the firearm, and more factors in that poor woman's control and under her moral responsibility when taking up a lethal weapon could have prevented this event. She is dead, but it could have been the child, or another innocent in a nearby shopping cart.