Lets analyze that basic statement for a moment but in a basic way, not in detail of a thousand different ways it could happen.
The officer is in front of a vehicle that needs to be stopped for either enforcement of the law (catch a law breaker) or to protect the public (someone about to drive drunk, etc).
The operator of that vehicle is able to see that the officer is in the way of the stopped vehicle and instructing the driver to stop.
The operator begins to drive towards the officer in obvious defiance of the previously mentioned fact thereby placing that officer in danger of death or serious injury
Now play the role of an officer, either the one in front of the vehicle in danger or the partner of the officer in danger. Would you fear a vehicle about to run you or a friend over? Would you just assume that he is going to accelerate quickly at you but stop inches before hitting you?
To be clear we aren't talking about some little old lady who is hard of hearing, the last few vehicle shootings were not some case of some innocent person with bad driving skills. The most recent Waikiki case we had a drunk person who showed an inability to drive, a refusal to listen to the officer, the continued attempt at driving (in a crowded area), a second crash and a third attempt at driving. In that case not only do you have a situation of the officer fearing his own safety but you have a situation where the operator of the vehicle poses a very serious threat to motorists and pedestrians. That driver had multiple chances to stop his car and comply with the officer's instructions yet he continued to ignore them.
OK, let's use that last example, and I'll do it the "old fashioned way".
I observe the car in front of me run into the back of a bus. I turn on my flashers, get out and approach the vehicle. I ask the driver "What happened there buddy?" He responds with an expletive and takes a pull from an open beer he's holding. I lean into the vehicle, and explain that drinking and driving is illegal and ask him to shut off the car and get out for a sobriety test as he's obviously drunk. He responds with another expletive. I then crack him twice, hard, in the side of his head, reach over and shut the car off. I open the door and try to remove his safety belt, he begins to resist, I hit him, hard, again, then I yank his drunk butt out of the vehicle, throw him face first onto the pavement, put a knee in his back and cuff his ass. I then drag his drunk butt over to the curb and deposit him to await the cruiser that I've just called to transport him to the cellblock for booking, I read him his rights and I call a tow truck. Now all that's left is the paperwork.
Pretty neat huh? The really cool thing is, nobody dies. My hand is a little sore, but other than that, I'm feeling pretty good about the outcome.
You can't tell me he couldn't have done it that way because I saw the video of the incident and I've seen similar incidents play out in the same fashion over the years.