People protesting the killings of Alton Sterling and Philando Castile march through Times Square on Thursday evening.Eduardo Munoz / Reuters

When Philando Castile was shot to death on Wednesday, he was in his car, restrained by a seatbelt. When Alton Sterling was shot to death early Tuesday morning, he was in the parking lot of the convenience store where he sold CDs, pinned to the ground.

This is what two amateur videos—filmed by trained bystanders or courageous loved ones—appear to reveal. Twice this week, Americans have found themselves reduced to outrage and mute grief by the killing of a black man by a local police officer. It happened on Wednesday, and then again on Thursday—just as it also occurred last December, and last August, and last July, and last April, and last January, except the “man” in that final instance was a 12-year-old boy. Expand the count to include black women and Hispanic men and the number of incidents nearly doubles.

These are not the only Americans who were killed by cops last year. More than 1,000 people are killed by police officers every year in the United States, according to The Washington Post and The Guardian. And as my colleague Vann Newkirk II writes, a black American will be killed by an officer every two days.

What makes these deaths different—what makes them subjects of public grief, warranting a Facebook post from the president—is that they were filmed. Alton Sterling and Philando Castile became news not because of the uniqueness of what happened to them, but because a camera documented their suffering and death. Journalists, lawmakers, and the public see the footage, and they believe.

Neither of these two videos were produced by luck or happenstance. In Baton Rouge, an activist group called Stop the Killing captured the film of Sterling’s death. According to Wesley Lowery of The Washington Post, Stop the Killing monitors the police scanner to intercept and film potentially violent encounters between local residents and officers. Volunteers heard chatter about the convenience store early on Tuesday and drove to the scene.

But despite filming the killing, the group did not immediately release the video because they wanted to see how police framed the incident. “You want to see what the police are going to say and how transparent they’re going to be,” Arthur Reed, the group’s leader, told Lowery. Only after the incident was not publicized did Stop the Killing publish the video to Facebook and Instagram.

In Minnesota, the situation was different but just as intentional. Castile’s girlfriend, Diamond Reynolds, was a passenger in the car when it was pulled over. After the officer shot Castile, she began streaming the incident using Facebook Live. In a resolved and steady voice, she describes what precipitated the shooting.

“We got pulled over for a busted taillight in the back,” Reynolds says. “And the police, just … they killed my boyfriend. He’s licensed to carry. He was trying to get his ID and his wallet out of his pocket, and he let the officer know he had a firearm and was reaching for his wallet. And the officer just shot him in his arm.”

Reynolds’s purposeful decision to document the aftermath of the shooting—despite her boyfriend dying next to her, despite her daughter sitting in the backseat—is why this shooting is a news event today.

It was a mark of her foresight and composure that she chose to livestream the event rather than film it to her phone. Livestreaming the moment immediately stored it on Facebook’s servers, preserving it even if her phone were confiscated or destroyed. For the same reason, the ACLU of Southern California created an app last year that immediately uploads video of police encounters to its own servers.

So many videos of black death have circulated that there is now the question of whether they are changing the public’s mind at all. This is not the first moment in American history when photography has made it possible for mass, often-white audiences to grieve the deaths of black strangers. It’s a commonplace that the images of Emmett Till’s brutalized body, published in 1954, galvanized public support for the civil-rights movement. The photos of 15-year-old Elizabeth Eckford attending Little Rock Central High School in 1957, and the police brutality that faced the 1963 Birmingham campaign, further changed white Americans’ minds. But even then, the Civil Rights Act was not signed until 1964.

“That’s a decade, right? A decade’s worth of impactful visuals,” says Danielle Allen, a political scientist at Harvard who has studied how the Civil Rights Movement altered American citizenship.

“But then you have to ask the question of what’s happening alongside that. Even before Emmett Till, the NAACP was already engaged in legal work of a variety of kinds,” she said. There were also many successful state-level policy campaigns before the federal statutory changes of 1957 and 1964. “I think the biggest challenge we have now is that people are having a hard time figuring out how to understand the relationship between state law that needs to change, and federal law that may or may not need to change,” she told me.

In other words, while there may be national outrage at the videos, state-level changes may be what is most needed first. Mass shock and outrage do not translate into reform, and knowing something is wrong is not the same as understanding what is wrong or how to fix it.

The American public has also not yet sufficiently discussed whether policing reform (such as introducing body cameras) will be enough to stop the killings, or whether the country must substantially alter the criminal-justice system and end the drug war, Allen said.

That uncertainty makes it likely there will be more deaths, and more videos, and more days of mourning. More family members, bystanders, and volunteers will make the intentional decision to document the tragedies unfolding before them. But even as videos proliferate, not every victim of police violence will be filmed, and not every anguished friend or neighbor will have the wherewithal to pull out their cameras.

As many people noted on Twitter on Thursday, the circumstances of both Sterling and Castile’s deaths might seem unbelievable without the video evidence—especially to those who lack personal experience with police brutality. Only because the videos exist is the wider public permitted to believe. American democracy will be all the stronger if Americans can recognize that sometimes they will never be able to see—yet must still believe.

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