Why would you be standing there holding a gun at the innocent? If you need to draw and fire, putting rounds into the perps, the cops will arrive and see them on the ground and the building nearly empty.
As a CCW, former MP, I'm not hanging around for the cops to come in blasting anyone with a gun raised. Right back into the carry holster as I exit the scene along with the last few who didn't already get out.
The Sherriff is Monkey Dancing - expressing verbal comments to maintain his impression he should be the Alpha male and dominate the social ranking. HE WON'T EVEN BE ON THE SCENE for at least a half hour after it's all over. He's not going to put anyone down or even have his service weapon drawn - that will be a much lower ranking cop on patrol with backup and a good ten minutes after the gunshots are done. It's purely political posturing on the his part to impress the pro-gun lobby that he thinks he's in charge of every crime scene. Regardless that it will happen while he's standing at the coffee machine enjoying his afternoon Crispy Crème.
As for the Hero who actually draws to defend himself - only if your exit was blocked by the gunman directing his weapon at you. Your primary tactic should be just the same as anyone else there - make distance, get behind cover, plan retrograde movements, get the out of there. Going toe to toe with a nervous gunman strung out on adrenaline, withdrawal, or whatever drug of choice they took to get up to do the crime is dealing with an irrational human on the edge. Think about it, veteran husbands, we even tip toe around the wife at certain times. Discretion is the better part of valor.
Nonetheless - if you draw a gun during a bank robbery and elevate the situation to gunfire, then there is a very real risk that a Good Guy WILL get shot. AKA the Walmart Hero, who was gunned down from behind by a second shooter. People armed exchanging gunfire in street clothing cannot and will not know who is a "Good Guy," and the police coming into that firefight won't be any better at it either.
Entirely the point of what the Sherriff was saying - think twice about pulling a gun and going Hero in the situation. You ARE elevating the risk of getting shot, when all you were trying to was bank some cash or get a loan. Whatever you were there for isn't worth dying over, and whoever is robbing the bank isn't likely going to get much in cash - they could be there to establish some gang credibility and your dead body is what they may be needing. Why hand them the decision point?
Tactics state you shouldn't even be trying - deescalate, make distance, get out of range. Look to what the Sherriff was warning you about, even tho it's really meant to thump his chest as the Alpha male. There actually is some tactical lessons to learn from there and his advice isn't off the mark when you think about it.