The police and Pritchard’s video were so different as to resemble alternate worlds. The police had claimed three men approached Dziekanski. The video showed four. The police had claimed that Dziekanski was reaching for something on a desk when he was tased, as if preparing to assault the officers. The video showed he wasn’t. The police said they couldn’t have pepper-sprayed Dziekanski, as too many other people were nearby. The video showed that a plexiglass wall separated Dziekanski and the officers from anyone else in the airport.

The video made a difference.

Just last month, Benjamin Robinson was found guilty of perjury.

* * *

Three days ago, a local newspaper in South Carolina reported the police explanation for the shooting death of an unarmed black man, Walter Scott, as he fled from a routine traffic stop in the town of North Charleston. From The Post and Courier:

A statement released by North Charleston police spokesman Spencer Pryor said a man ran on foot from the traffic stop and an officer deployed his department-issued Taser in an attempt to stop him. That did not work, police said, and an altercation ensued as the men struggled over the device. Police allege that during the struggle the man gained control of the Taser and attempted to use it against the officer. The officer then resorted to his service weapon and shot him, police alleged.

The Post and Courier also quoted a confused cousin of Scott’s: “He’s not a violent guy—never seen him argue with anybody. I just can’t see it,” Samuel Scott told the paper.

Then, on Tuesday, both The Post and Courier and The New York Times obtained videos of the shooting. They showed a different story.

The video shows the officer, Michael T. Slager, shooting Scott as he runs away. Slager does not start firing—eight times, at Scott's back—until Scott is fleeing. The video then shows Slager dropping an object on Scott’s body. It isn't clear whether this object is a stun gun. Finally, the video shows sets of officers arriving on the scene in the minutes after the shooting, and it shows none of them attempting CPR.

On Tuesday evening, Slager was charged with murder.

* * *

In the past year, after the killings of Michael Brown and Tamir Rice, many police departments and police reformists have agreed on the necessity of police-worn body cameras. Body cams seem to be good for everyone. By creating a better record of officer-citizen interactions, the argument goes, they protect cops from unfounded accusations and give citizens a kind of justice insurance policy.

But the most powerful cameras aren’t those on officer’s bodies. They’re those wielded by bystanders.

We don’t yet know who shot these videos of Slager, who carried these tools of witness. But unknown cameramen and women lived out high democratic ideals: They watched a cop kill someone, shoot recklessly at someone running away, and they kept the camera trained on the cop. They were there, on an ordinary, hazy Saturday morning, and they chose to be courageous. They bore witness, at unknown risk to themselves.