The question we all have to ask is what potential situations exist that mean deadly force is needed right now. Clearly those situations may involve minors employing deadly force. Most of us humans have some degree of difficulty with the idea of causing the death of another person -- and more difficulty with causing the death of a "child". We instinctively want to protect the weakest among us, and children are part of that weakest group usually. Noting this difficulty with causing someone else's death, warriors have long dehumanized their enemies because that made it easier to rationalize killing them. It makes them more effective warriors.Tremendously sad, on both fronts. Frankly, this has always frightened me as a self-defense scenario: a kid. Just a kid and this one barely out of puberty. If a shot is fired, I'm pretty confident I'd do what it takes to stop the threat. But if it's a 12-year-old kid holding a gun and he hasn't done anything yet? I know I'm likely to hesitate, maybe a lot--maybe far, far too long--before using force.
A few decades back, I enjoyed reading the articles written by Col. Jeff Cooper in gun magazines. He always called assailants Goblins, essentially dehumanizing them because they had stepped outside the social contract and used violence without provocation on others. For me, part of the "trigger" mechanism for employing deadly force is what actions cause me to view an actor (human or otherwise, age and size relevant only if there are clearly no force multipliers) as a deadly threat -- a Goblin, if you will -- and immediately employ the force necessary to prevail over them.