The problem is that the police already know that being forced to get out of your house or car by a stranger without any logical reason is going to alarm or raise flags with most anyone. There isn't an excuse for murdering someone because you feel like you should be simply obeyed for exercise of arbitrary power. If the behavior of one employed as a police officer is questionable then his or her motives and lawfulness may also be just as questionable.He tells Bryce to get out but doesn’t give a reason. Bryce repeatedly asks if he is under arrest. Runnels says, “You’re under arrest. Get your ass out of the car,” and attempts to pull him out by force.
In that particular case, the one employed as a police officer allegedly smelled 'weed' and the MASTERS failed to get out of his car or to roll down the window after being told to get out of the car. The smell of weed apparently was a key factor, the failure of MASTERS to comply with the officer is another.
Officer's Report (PDF)
P.S. In St. Louis City, Missouri, a civilian board for police oversight was established despite opposition from police.