Someone who has rarely shot a gun before might as well fight unarmed. When something goes bump in the night it creates a serious rush of adrenaline and fear. Grabbing a gun you've barely touched, much less shot is dangerous. As stated before, when going against unarmed assailants they lose any advantage they would have by staying on the defensive. If they come face to face with an intruder, a inexperienced mistake like leaving safety on, being unloaded, or mentally freezing could be deadly.