In the heat of the moment and while in a defensive situation, anything can happen. No one can really know how they’d react until that moment comes.
In the above video, we see a security guard stop two armed threats, and he does a pretty good job in the beginning.
But when bad guy #2 is down due to a few shots from the security guard, that doesn’t stop the guard from continuing to fire.
One important thing to remember is that once the threat is no longer a threat, that’s your cue to stop firing. By all means keep your firearm trained on that now-down threat, but if you’ve successfully incapacitated them, it’s time to stop throwing lead.
This can lead to a world of trouble in the legal system, and an otherwise good shoot can turn bad in a hurry.