When I was a LEO firearms instructor, we would discuss what would happen if a bad guy and an officer would draw and point at each other at the exact same time... what would happen?
In the high majority of cases, the officer would be shot first. The reasoning was based on the morality of each shooter. Most police officers come from a middle-class-morality based environment. The crook comes from a low-class-morality base. This has nothing to do with financial standings. There are very high-class-morality based people in poverty (Mother Theresa), and very low-class-morality based people in the upper crust of finance (Bernie Madoff, etc). It all has to do with what values are being held.
Most police officers value life and property, while the crook couldn't care less about anything but themselves. So, both guns are drawn, aimed, and the officer goes down first. That's why reactionary shooting must be indoctrinated into the officer. When the LEO sees the threat, he must instinctively shoot it. Preferably multiple times. Don't ever think that the bad guy is going to have a revelation, "I better lower my gun. That's a cop!" No. He's going to think, "F-U. BANG!" All the while, the poor officer is thinking, "I don't want to shoot him. I hope he drops his gun." Then it all goes dark. It all happens in mili-seconds. If you have to think about it, it's too late.