This one is different.Walter Scott was killed — shot multiple times in the back — by North Charleston, S.C. police officer Michael Slager last weekend. Scott, already running away, was no threat to the officer when the first shot was fired. He was even less of a threat when Slager paused and fired the eighth and final round.To non-police, Scott's death may look familiar: Not even a year after Eric Garner died during an arrest in Staten Island, N.Y., and Michael Brown died in a police shooting in Ferguson, Mo., here was another black man killed by police.But to law enforcement officers observing the North Charleston tragedy, the case is nothing like "another Ferguson" — and that's where the police perspective and the civilian perspective on these events diverge.In Ferguson, as the Justice Department made very clear, all credible evidence supported officer Darren Wilson's account of a justified, legal and necessary shooting. Brown robbed a store, fought for the police officer's gun and then physically charged the cop. In North Charleston last weekend, all Scott did was drive with a broken taillight and run from the cop who pulled him over.Like Scott, Garner died on camera as a result of police actions — in Garner's case, a chokehold was used during his arrest. But most police officers see very little similarity. There's a tremendous moral and legal difference between a person dying during an altercation with police and an officer willfully using lethal force. Policing can be bad and mistaken, both tactically and morally, and still not be criminal. Garner's and Scott's deaths were both tragedies, but only Scott's was a crime.To see a black life snuffed out by a fellow cop is especially painful to police officers who spend much of their careers trying to protect black lives. One New York City officer wrote me to say, "This cop also just shot all of law enforcement in the back." At home and in roll calls around the nation, cops watched the video of Scott's killing and cringed not only at his death, but also at the officer's betrayal of the police uniform and everything it stands for.Police officers in general, myself included, were initially less concerned when Brown was killed. "Witnesses," many of whom didn't see the actual events, will inevitably lie, contradict and blame the cops. That's to be expected, not believed. Too often, the public criticizes police for using any force at all or simply doing their job. Brown had robbed a store: Absolutely, he might fight an officer to avoid arrest. Sometimes people do fight cops, and sometimes cops need to fight for their lives. To police, Wilson's account rang true.Without the North Charleston video, most cops would have similarly given Slager the benefit of the doubt. When things go wrong, they go wrong quickly. Sure, it's easy to imagine many ways in which a situation could have been handled better. That's the luxury of hindsight. Cops need the benefit of the doubt to do their job. But it wasn't so much that Scott was unarmed — unarmed people can kill, too — it was that Scott was running away.When I was a cop in Baltimore and I heard of some situation that got ugly, my first reaction was usually, "Thank God I wasn't there." Because nobody knows how they'll react. For that reason, most police officers are quite reluctant to criticize others forced to make split-second life-and-death decisions. Yet every police officer I've spoken to says that Scott's death was horrible and that Slager committed a crime.In 1985, the Supreme Court ruled that police may not shoot at unarmed fleeing suspects, even felons. In line with that decision, shooting without an immediate threat is against the law in every state, and it's against department policy in every jurisdiction. It's also a violation of the most basic human right: life. Any innocent death is a tragedy, but it's worse at the hands of police. It's not too much to ask our civil servants not to murder us.During his attempt to catch Scott, Slager fired his Taser. When that failed, Slager could have chased Scott or let him run away. But instead, Slager drew his gun and shot. This is why cops see this case so differently: The criminal was the police officer. And Slager was arrested and charged with murder. That is the way the criminal justice system is supposed to work.What the deaths of Garner, Brown and Scott do have in common are individuals who didn't want to go to jail and cops who wanted to take them there. So one logical way to reduce potentially deadly arrest situations — whether the deadly force involved is justifiable, questionable or criminal — is to stop criminalizing so many people. More productive than blaming police for enforcing existing laws would be to change and soften our laws in a way that does not jeopardize public safety.Many jurisdictions actively punish people, poor people in particular, with fines, tickets and court fees. And this disproportionately affects African Americans. We need to stop seeing the criminal justice system as a source of revenue. We need to actively decarcerate and end the racist war on drugs. We need to fight the poverty, violence and illegal guns that have destroyed entire cities.But we can start small. Every time a civil or trivial matter becomes a criminal matter, police are put in the position of becoming the bad guys. Selling "loosie" cigarettes need not be illegal. It could be legal and regulated. Minor vehicular violations like the broken taillight for which Scott was pulled over could be a matter for state inspectors rather than local police officers. Monetary fines could be indexed to reflect a person's income or wealth. Civil fines should never escalate to incarceration. Nobody should be jailed for being poor.This is society's problem. It goes beyond the police. Still, it's hard to fathom how anybody could shoot a fleeing Walter Scott in the back.— Special from the Washington Post. Peter Moskos, the author of Cop in the Hood and a former Baltimore police officer, is an associate professor at John Jay College of Criminal Justice.