The official story out of Balch Springs, Texas last week was that a police officer had been forced to fire into a carload of black teenagers, killing a 15-year-old passenger, because the car was being driven in an "aggressive manner" toward the officer, giving him no choice but to defend himself.

Only after video evidence emerged did police officials alter their story. The new version acknowledges that no officer had been endangered, and that the vehicle had been moving safely away from police when the deadly shot was fired. Commendably, the officer who fired the fatal shot has been discharged and may face criminal prosecution.

The dead teenager was named Jordan Edwards.

"He was everybody's friend — his attitude and smile, everything was just contagious about him. He was excellent — 3.5 GPA, never in trouble, no attendance issues," Jordan's football coach said. "He was a kid that did everything right."

In Gwinnett County last month, police officers pulled over a black motorist for a traffic stop. After the motorist emerged from his car as ordered, with both hands raised, he was punched in the face. Later, when the motorist lay helpless on the ground, handcuffed, a second officer rushed up and stomped on his head.

According to initial police reports, neither incident happened. Only when cell-phone video evidence emerged did the police story change, forcing the firing of the two officers. To the credit of Gwinnett officials, both have since been charged.

And then of course there's the infamous, tragic case of Walter Scott, the 50-year-old black man shot down in his tracks by an officer in North Charleston, S.C.

That too was initially explained away as an official case of police self-defense, at least until a citizen video emerged documenting otherwise. Even with that evidence, a South Carolina jury failed to convict the officer, who this week agreed to plead guilty to a lesser charge.

In each of those cases, and in too many others, only video evidence allowed the official police version to be challenged, let alone disproved. Without that evidence, valid claims of police brutality and indiscriminate use of deadly violence would have been treated the same way they had been treated for decades -- whitewashed, condemned to echo as powerful oral history within the black community while the larger culture ignored them as urban myth.

Even now, only a small percentage of police/citizen interactions are videotaped, ensuring as a matter of mathematics that a lot of these cases continue to occur. For example, one of the officers involved in the Gwinnett brutality case had 67 previous use-of-force incidents on his record, several of which resulted in claims of excessive force. Only the existence of civilian video changed the outcome in the most recent case and got that cop off the street.

Here's my fear:

Summer is coming on, and with it an increased chance of such encounters. In the past, the U.S. Justice Department has served as a helpful arbiter in calming local outrage and ensuring that a fair investigation is carried out. I'm not sure that it's capable of playing that role any longer, or even has an interest in doing so.

Instead, U.S. Attorney General Jeff Sessions has made it clear that he has little sympathy for those concerned about excessive police violence. He has ordered a review of all consent decrees between the Department of Justice and local police departments -- decrees reached because the departments had demonstrated, proved problems -- with an eye toward freeing those agencies from federal oversight.

"(Such consent decrees) can reduce morale of the police officers," Sessions explained. "They can push back against being out on the street in a proactive way."

President Trump, elected in part by a white backlash, has also advocated a more aggressive, less patient approach to protests and civil unrest in the wake of police shootings, accusing groups such as Black Lives Matter of instigating assassinations of police officers.  That combative attitude regarding a very real and serious problem, in an already highly charged political environment, could prove to be an explosive combination in the summer of 2017.

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BTW, here's a video response to the Gwinnett case posted by Lt. Tim McMillan, an officer in the Garden City, Ga., police department: