how would you sustain them?
You do have a point.
I mean one of the cops who heard the backfire probably crapped a load in his pants, a feeling so offensive that the only way to make him whole again would be to call in his gang in blue and do whatever it takes to bring death to those who dared to accidentally bring momentary quivering cowardice to the officer's bowels.
Charging the police is wrong, heck they should all be getting medals for their shooting prowess that kept their stray bullets from penetrating houses and killing a 4 year old or her grandmother in their sleep. This is the sort of training and dedication that really seperates the cop in hot pursuit of a tune-up offender from the average gangbanger doing a driveby.
Then there's the issue of officer safety. The driver of the car obviously tried to run down a cop with the car, or maybe even conspired to run one over by driving on the same street as a cop. Our knights in blue are worth more than a serf, heck worth more than a 1000 serfs. The passenger of the car probably gave the cop a dirty look which probably caused a spike in blood pressure to the cop, if the cop was a corpulent donut eater, well officer safety again.