Completely untrained yes but there’s lots of people with these skills. I do IDPA matches with my son at a tactical range near Waxahachie TX, people there do these kinds of drills constantly. There’s also lots of ex-military instructor led close quarter and urban combat training available to anyone. Combat trained random people are probably more common than you think. It’s sort of like martial arts, some people are just really into it.

> I do IDPA matches

Yes, this is the level of training I imagine as sufficient. A match applies pressure: you're on a clock, there is an audience, you have a safety regime and people scrutinizing you on it, and at the end, there is a score. I don't claim Fort Benning sniper school is necessary. Only that you likely can't just wander out of a gun shop with your scoped deer rifle at any price and snipe targets at range under pressure: there is more to it than the weapon.

> Combat trained random people are probably more common than you think.

I listed a wide variety of people with the training I believe is sufficient.