Moments after a police officer shot Philando Castile, his girlfriend Diamond "Lavish" Reynolds called for help. Not to 911--Castile's shooter after all was a representative of law enforcement--but to the only other lifeline Reynolds had: her friends and family on  Facebook.

"Stay with me," Reynolds says as her Facebook Live stream begins and pans over to show her boyfriend covered in blood. It's a choice of words that applies as much to her dying boyfriend as the audience she's trying to reach.

Reynolds streams the event, describing the situation throughout the 10-minute stream, all the while calling for help. "I ask everybody on Facebook, everybody that's watching, everybody that's tuned in: Please pray for us."

Using Facebook Live, Reynolds immediately began broadcasting the situation to her entire network of loved ones. Reynolds, an African American woman whose own life in that moment was being threatened by the police officer just as Castile's had been, used the live-streaming tool in a way that it's hard to imagine a white man like Mark Zuckerberg would have ever thought to: She used it as her own social 911.

"What Lavish Reynolds did set a precedent. It goes beyond just taking a video, because in real time maybe it could potentially help save a life or make an officer think twice about their actions," says Everette Taylor, an African American tech entrepreneur and the vice president of marketing for Skurt, a car renting app. "I could potentially see a minority stating when getting pulled over or in another predicament...that they are recording the events live. I think this will change how some officers act."

It's been almost two years since the killing of Michael Brown in Ferguson, Missouri, and the rise of the Black Lives Matter movement. At the time, those shootings were just beginning to re-enter the consciousness of the mainstream media, and it was in large part due to all the chatter around them on social media. But while footage and photographs of the ensuing protests dominated Twitter,  Facebook's News Feed ignored much of the early Ferguson saga in lieu of other viral topics, like the Ice Bucket Challenge.

Since then, coverage of the shootings has only risen thanks to the exploding accessibility of  smartphone video, which has helped victims and witnesses capture these horrific moments and upload them after the fact on social media. But as live streaming video apps have proliferated in the past year, the coverage of these moments and the power of these tools are beginning to change once again. Not only are these apps recording, they are instantaneously broadcasting officers' actions and victims' pleas for help to the world.

"When you feel like you've been racially profiled and have just witnessed the police murder your boyfriend, who do you call? The police?" asks Shaun King, a civil rights activist and senior justice writer for the New York Daily News. "We've reached a strange point in history where our social-media streams are becoming something akin to our own versions of 911."

Social media shouldn't have to provide this sort of accountability. That's what the body- and dash-cams used by so many police departments around the U.S. were designed to provide. All too often, however, those cameras fail, as they did when they fell off of the police officers involved in the Baton Rouge, Louisiana, shooting of Alton Sterling earlier this week.

"Body- and dash-cams aim to do this but are too often turned off or not used at key moments because bad cops are smart and don't want their actions recorded when it's so much easier to make up facts," says Sarah Kunst, a Silicon Valley entrepreneur and the founder of Proday, a fitness app. Kunst is an African American woman and often works with civil rights leader Rev. Jesse Jackson. "Citizens become the truth tellers who record and hold accountable the bad cops and the systems that leave them in power."

Among these livestreaming tools, Facebook Live has emerged as perhaps the most important for these types of incidents. There are countless livestreaming apps out there, including Twitter's Periscope, but Facebook has two key advantages. While other streaming apps require you to build a new network of followers or somehow hope your stream goes viral, Facebook Live is already tapped into your existing network of friends. Secondly, Facebook has more than 1 billion mobile users. For many people, there's a good chance the only livestreaming app on their phone is Facebook.

So what should you do if you find yourself in a situation where you are threatened by a police officer? Open the Facebook app, tap the "What's on your mind?" field, hit "Live Video," start shooting, and tell the police officer "I am broadcasting this video live."

"There are sweeping structural and legal changes that need to be made, but that takes time these victims do not have," Kunst said. "In the meantime, today, let's start with using the technology we all have in hand to make it more likely that the next wannabe killer cop slows down to think before he acts."