The killing of Alton Sterling at the hands of police in Baton Rouge, Louisiana, has sparked national outrage after a video showing the incident was posted online Tuesday night. That video was the result of an organized effort by local activists, who use smartphones to monitor and record violence.

A nonprofit group in Baton Rouge, known as Stop The Killing, tracks crime through police scanner apps. The Washington Post first reported news of the organization's activities. When members of the group hear about an incident, they drive to the scene to document it, recording and producing videos to draw attention to violence in the community.

"We just try to bring awareness to what's going on."

"We just try to bring awareness to what's going on," the head of the group, Arthur "Silky Slim" Reed, told The Verge in an interview. He says the group is not specifically focused on incidents of police violence, although the group has taken footage of it before.

Sterling was outside of a convenience store where he sold CDs when he was shot and killed. Police said they were responding to reports of a man with a gun. The video captured by members of Stop The Killing shows Sterling pinned down by shouting officers, who draw their weapons and point them at Sterling. Multiple gun shots go off as someone behind the camera gasps. The camera pans away, although a second video, taken by the convenience store owner and released later, shows Sterling bleeding. No gun, besides the officers', is immediately visible in either video.

Reed says there are seven or eight people in the organization that all regularly listen to the scanners — several different versions of police scanner apps of those that are publicly available — for reports of violent crime. "Sometimes we get to crime scenes before police," Reed says.

The group has a documentarian arm known as We Shoot First Films

Stop The Killing tries to record a scene three or four times a week, Reed says, and has uploaded some of its footage — much of it showing graphic incidents of crime scenes — to YouTube. The documentarian arm of the group is known as We Shoot First Films, and has produced a series: To Live And Die In Amerikkka.

After recording an incident, the group takes the footage and produces videos, distributing them to schools and prisons in an attempt "to wake those individuals up by the images that we have shown them." That, Reed says, was how the Sterling shooting was first recorded. Members of the organization heard about the incident through a scanner app, drove to the scene, and recorded what they saw. (Reed declined to provide some details, such as who was recording the shooting, or how many people were present at the time, saying the organization has safety concerns. "We just feel satisfied that the story is told," he says.)

The group did not immediately release the video, Reed says. Instead, they waited for the police's response, but afterward, decided it needed to be publicly shown. "We didn’t like what we saw, but we knew we couldn’t believe the police," he says. So the group brought the video to the local news instead, then to the Associated Press. On social media, the video became a major viral news story.

Peaceful protests have started around Baton Rouge, and the officers involved have been placed on leave. The Justice Department has since said that it will investigate the shooting for civil rights violations.

A second, clearer video of the shooting has since emerged

The way the video was captured reflects the changing ways that incidents of police violence have been recorded, as footage of police shooting black men has continued to make headlines around the United States. A national push to offer police body cameras to record such incidents has gained some traction, but there continues to be questions over who controls the footage. In the case of the Sterling shooting, police told reporters that the cameras were somehow dislodged, but did continue to record. Yesterday, as news of the Baton Rouge shooting continued to unfold, a second video showing the aftermath of a deadly police shooting in Minnesota was streamed live through Facebook. That video showed a black man, Philando Castile, dying in a car after being shot by police.

Police in Baton Rouge have said they are reviewing video from the incident. Reed says the video taken by Stop The Killing — combined with the second video — is enough to make clear what happened in the shooting.

"The video speaks for itself," Reed says.