here is an informative article-- seems fairly unbiased and explains the officers rights:
http://www.vox.com/2014/8/13/5994305/michael-brown-case-investigation-legal-police-kill-force-murder
"But each use of deadly force does have to be evaluated separately to determine if it was justified. "The moment that you no longer present a threat, I need to stop shooting," said Klinger. According to the St. Louis County Police Department's account, Wilson fired one shot from inside the police car. But Brown was killed some 25 feet away, after several shots had been fired. To justify the shooting, Wilson would need to demonstrate that he feared for his life not just when Brown was by the car, but even after he started shooting. The officer would need to establish that, right up until the last shot was fired, he felt Brown continued to pose a threat to him whether he actually was or not.
"There's a difference between the moment you cease to be a threat and the moment I perceive that you ceased to be a threat," says Klinger. And Katz points out that if an officer has been assaulted and the suspect runs away, the officer's threat assessment is probably going to be shaped by having just been assaulted. But, Katz says, "one can't just say, 'Because I could use deadly force ten seconds ago, that means I can use deadly force again now.'"
