as a police officer with the potential to end a life in an instant, you're not supposed to go into this situation ready to shoot anything that remotely looks suspicious. its obvious that if this kind of stuff can happen that easy, they need to be trained differently, or there needs to be some sort of measure the police take first before immediately shooting.
When you're a cop, you'd realize these types of situations can go south extremely fast, which is why you have to be ready to take action no matter the situation.
If you go to a situation as a cop expecting everything to be okay and nothing will happen, then you are trained wrong. If you are a cop and you go into a situation knowing that it can go bad very fast and you have to be prepared, then you're trained correctly.
As a cop, you
have to be ready and be able to think on your feet and take action against things that look deadly or suspicious, especially when it seems like the guy is legitimately holding a gun.
It can be this fast: *pulls a guy over, the guy gets out and is holding something thats black in a suspicious way that looks like a gun and got out very awkwardly* "gotta follow pro-" *the cop is shot*