It's not self-defence to shoot people if the only reason they're approaching you is that you pointed a gun at them or someone else and they're attempting to disarm you because it appears that you're about to shoot someone or just shot someone. Otherwise anyone with a firearm can just point it at whoever and if they react at all, have free reign to shoot them. In fact, it's illegal to point a gun at someone else in the first place unless they're already attacking you (or in some states have entered your property), and Rittenhouse pointing a gun at someone else was the trigger for the whole incident. If he'd been charged for pointing a gun at people, then the second-degree murder charge would have stuck, as self defence isn't a defence against second-degree murder (otherwise a home invader could claim self defence if they shot the homeowner when confronted).