I don't have a specific side in the case but I wanted point out there is a HUGE difference between the "we don't need you to do that" that was said and a clear "stop following him". Think of a time you've told someone "you don't need to do" something, the only things that come to mind is my wife trying take out the garbage, or friends helping clean up after having people over, it usually said to someone who thinks they are doing the right thing and helping. If someone is doing something wrong, like keying my car, or stealing something I wouldn't say "you don't need to do that" I would say "stop!" the police ARE the authority and when they had the chance they never gave him the "stop" command that a person with authority could/should have.
If an authority figure gave him a "stop" command he either would have stopped and te killing would have been avoided, or he would have gone against a dirrect police order which would have made this alot more cut and dry.