The robbers started this with an advantage of initiative, numbers, preparation and mental preparedness. This is why the ambush is the most effective form of attack. If the shop owner were to react at this time, he would lose the majority of the time.
This shop owner feigns submission, waiting until the robbers are no longer focused on him and draws to fire when they are at their most vulnerable. This is a counter-ambush.
A fairly inept man drops his knife and is controlled effectively when this woman pulls his hoodie over his head. This gives her handles to control his posture, obstructs his vision and limits the mobility of his arms at the same time.
A passenger intervenes to choke out a belligerent drunk man who is arguing with airline staff. The choke quickly and effectively ends the confrontation.