Baton Rouge, Louisiana – Over the past decade, a Baton Rouge anti-violence group has filmed the aftermath of more than 30 deadly shootings in the city.Its most recent video, capturing a police shooting that killed a black man outside a convenience store, has reverberated far beyond Louisiana's capital.Founder Arthur "Silky Slim" Reed said during an interview on Wednesday that members of his organisation, Stop the Killing Inc., were monitoring police scanners early on Tuesday when they heard a report of a disturbance at the store.Several members of his group drove there and captured video of two white Baton Rouge police officers scuffling with 37-year-old Alton Sterling before he was fatally shot."The video pretty much speaks for itself," said Reed, 43. "That officer executed him, is what we see on that video."Baton Rouge Police Chief Carl Dabadie Jr. said that Sterling was armed. The US Justice Department has launched a civil rights investigation into the killing.Reed said he wouldn't disclose the names of his group members who were at the scene of the shooting "for our own safety".Deadly forceHis group circulated the video by social media hours after the shooting, fuelling protests by dozens of people at the store on Tuesday night. It comes at a time when law enforcement officers across the country are under close scrutiny over what some see as indiscriminate use of deadly force against black people."The police never knew the video existed," he said. "Once (police) had their story out there and they told their story, then we put the video out there to contradict their story."Reed said he was a gang leader for years before he became an activist. "We're trying to save the next generation," he said during an interview near the shooting scene."One of the things that we see and you may hear out here tonight is that 'Black Lives Matter'. Our mission is to let black people know that black lives will never matter until they matter to black people first."Reed said he doesn't post any videos without first seeking permission from shooting victims' relatives.Michael Mitchell, who has worked with Reed for the past six years, said he believes the group's videos send a powerful message and "make a great difference"."We want to see things change," he said. "We need to be on the ground where things are happening."Reed expressed confidence that protests in Baton Rouge will remain peaceful, even as people from other communities join them."We're keeping a close eye on that too, because we don't want outside agitators to come and upset this whole thing," he said."That's not saying that anyone is afraid to rock the boat ... But at the end of the day, we would like a peaceful solution, and we would like to see justice take place here."Watch the video below. WARNING: Not for sensitive viewers.