Granted, not being able to distinguish between a lethal & non-lethal weapon seems like the sort of thing that should prevent someone being allowed to wield them. Though we can all be pretty sure that's not going to happen.
It's a bonkers situation. If the weapon mixup was genuinely what happened (I personally think it's more likely to be true than not from what I've seen) then it's an act of gross misconduct and negligence that lead to the death of an unarmed man. If it's a ruse, then it's outright murder.
I've had probably 20 hours or so of pistol shooting training, only some of which was with a Glock 17 so clearly not an expert by any stretch but one thing I think that is worth mentioning is that after a few hundred holster draws you stop being aware of the weight of the firearm in your hand. When you start becoming more used to what you are doing you don't even notice pistol at all. You don't look at the pistol when aiming. Imho opinions about the Taser being a different weight and colour to a Glock don't really shed much light on what happened. Imho it's perfectly plausible that a dangerous/reckless cop could fail to notice they had the wrong weapon in their hand.
Whatever happened, somebody died who shouldn't have died and I have no trust in the system either getting to the bottom of what happened or holding the shooter accountable.
Accountability is the start right? I.e cops facing consequences for harming others