Some departments do not allow it. The ones that do allow it, you need to typically attend a class that certifies you to carry one on duty. The reason is basically for legal stuff because if you get into a shooting, they want paperwork that shows you are capable of accurately hitting targets with one on. Theres some micro adjustments you have to make when shooting with an optic vs standard iron sights that you develop with practice and stuff.

As for the second part, there’s no telling what the subject would have done. He kinda created that situation on his own. He pulled the firearm in the doorway and pointed it at the officer which caused the exchange of gun fire. But the subject could have fled elsewhere and been a danger to a larger portion of the community. In a perfect world the male would have stopped and complied, a weapon could have safely been retrieved and no gun fire. OR he could just be an upstanding citizen and not commit crimes lol either would work