It's obvious you've never had a job on the streets - as a law officer, EMT rescue, fireman, etc. Perhaps you should for your own education and service to your community.
Get over the term "slowly." If someone is trying to get a better shot, does it matter that they are moving their gun "slowly" over the target? No, it is the action that counts.
When a car driven by a suspect/perp moves after being told to stop, turn off the engine (there is a BIG reason for that command), and hold up their hands - EVERYONE in the area is in IMMEDIATE danger. It doesn't matter at what rate the suspect is moving the car - that the car is moving is the danger. Usually when a suspect begins to "slowly" move the car - they are doing two things.
One - they are beginning to really panic or have gone into the "zone" of where nothing matters anymore and it is time to take someone with them. Two - they are lining up the car for a better shot.
Either case is extremely dangerous and about to become worse in a hurry.
That better shot may mean a better way to run back into the streets to put someone else in danger but more often than not, the moving car usually means a suspect/perp has hit a point of uncontrolled violence. That slow moving car is going to head toward someone and could get real fast, in a big hurry. Someone is about to die. 2. Do you think a citizen, who saw a car roll SLOWLY toward toward him, could shoot to kill the driver and expect to be cleared of wrongdoing, because a slowly moving car is a deadly threat that merits deadly force? I don't.
It depends. Is that citizen able to get away and is the driver of the car slowly turning to get a bead on him before accelerating. The circumstances would decide. There have been cases of assault with a deadly weapon - a vehicle - in citizen cases.
But you are overlooking major differences.
A police officer's life is regularly assaulted as part of his job. The threat is higher than for the regular citizen. Thus, his latitude for reaction must be higher. No one is going to try to kill you today. But when a cop walks out the door in the morning, he knows someone is going to try.
Secondly, the area of responsibility is different. A citizen has only his own life to protect. A cop has his own life, his partner, the rest of the officers on scene, the people in the neighborhood, and the rest of the community should a violent suspect continue his crimes. In a situation such as the article describes, the scene and the suspect must be brought into immediate control - or there is an immediate threat to everybody in the area. Because the threat is not just to himself, but to the entire community, the officer again must have a wider latitude or reaction.
I suppose it depends on how long the citizen was chasing the driver.
Do you enjoy taking things out of context? The police knew that they were pursuing a suspect who had a weapon and who had just committed an armed robbery, and who would probably do just about anything to try to avoid being arrested and eventually end up in prison. That is a bit of a different situation than if a person on the street saw a car slowly back up toward them without any information in regard to the driver of the car or the driver's motive at that particular moment.
You have to put yourself in the position of the officers. They are standing behind their car doors with their weapons pointed at the suspect's car. Suddenly the car starts to move towards them. They are sitting ducks if that car suddenly speeds up and smashes into their car, as they will be knocked to the ground and possibly run over by their own vehicles. You don't stop and estimate the speed of the vehicle or do the physics calculations on whether the vehicle has the requisite amount of kinetic force to knock you down and push your vehicle over you. You see the threat and you respond.
The fact that the perp had started moving his vehicle towards the officers was more than sufficient threat for them to use deadly force.
Just put yourself in their position. The car is headed for you, you don't know if he is going to punch the accelerator, all you know is that if you don't respond, you could be seriously injured or killed. The police did exactly what I would have done in that situation. Indeed, they did exactly what YOU would have done in that situation.