If you ever watch the documentaries that follow the police, especially in the states, it's no wonder that people don't abide by what the police say. There are usually two or three officers shouting contradictory instructions, "get on you knees", "lie down", "turn round" or "put your hands in the air". A moments hesitation in deciding what to obey and you end up getting shot.
YMF, that's the police version of events. Others have different versions - some say yes, the guy was driving away but not heading toward the police?
Bodycams ought to show who is telling the truth. If they were being driven at, then the cops are probably justified in shooting - though i'm sure they could have just moved out of the way. If the guy was merely trying to escape, then they were not.