When Mark Zuckerberg introduced Facebook live-streaming in April, it was with a cheery video from the launch room in which he talked about the great things people were already doing with the service.

There was a stream of baby bald eagles and a guy who went live while he got a haircut. The mundane could become the suspenseful, Zuckerberg said, because viewers wouldn’t know what would happen next. In the months since, Facebook has celebrated go-live successes that include a watermelon exploding under rubber bands and a mom howling with laughter while wearing a Chewbacca mask.

Now the live videos commanding the most attention are far from mundane — and the social-media giant is struggling with how to handle its position in the middle of disturbing news events.

A Minnesota woman, Diamond Reynolds, had the instinct to go live on Facebook in the aftermath of a police officer shooting her fiancé, Philando Castille, the second high-profile killing of a black man by law enforcement this week. Her live video put Facebook in the position of delivering crucial information about a politically and emotionally-charged moment, and the company didn’t quite handle it smoothly.

Facebook took the video down, then apologized and blamed a glitch before putting the video back up. The video now has more than 5 million views.

Zuckerberg made a statement on his Facebook page: “While I hope we never have to see another video like Diamond’s, it reminds us why coming together to build a more open and connected world is so important-and how far we still have to go,” he said.

By Thursday night, hours after Zuckerberg’s statement, Facebook’s live video service again played a role in a tragic and disturbing moment of breaking news. Witnesses in Dallas used Facebook to broadcast live footage in which the sound of rapid gunshots could be heard in an attack that would leave five police officers dead and seven others wounded. The deadly attack came during a protest over fatal police shootings of black men.

Zuckerberg seems to recognize that Facebook could be more of a hotbed for citizen journalism, just like Twitter has been since the Arab Spring protests in 2011. Twitter’s Periscope app for live-streaming has also seen its share of dramatic crime scenes. But when dealing with live content on a large scale, there are clear risks.

Graphic content is removed if it celebrates or glorifies violence, according to Facebook’s content standards. While there’s an exception for images of public interest or concern, such a decision requires quick evaluation — potentially by a computer algorithm taking action after viewers provided feedback through the site. Facebook is working on more sophisticated artificial intelligence solutions that rely less on community monitoring, but improved automation will take time.

The line is thin, and the instances of live graphic crime are becoming frequent. Last month, for instance, Antonio Perkins of Chicago live-streamed his own murder. Another man, a sympathizer with Daesh, also known as ISIS or the Islamic State, streamed threats after he allegedly murdered a French police commander and his partner. The French video was taken down from Facebook after several hours; the video of the Chicago killing remained.

In any community of 1.65 billion people, there are bound to be clear rule-breakers such as the underage teens in Milwaukee who used Facebook to live-stream group sex. Facebook has no perfect system for automatically catching those videos before they go viral or making sure the important ones stay up.

As Facebook promotes the live video feature and figures out how to monitor it more efficiently, more and more people have started posting newsworthy content. When shots rang out in Dallas, Facebook users like Michael Bautista risked their lives to film what was going on and take questions from their social network audience. More than 4 million people watched one of his videos, including Zuckerberg.

Reynolds, who turned to Facebook live video as her fiancé died from his wounds in the car seat beside her, explained to reporters that she wanted people to know the truth of her situation. “I wanted everyone in the world to know that no matter how much the police tamper with evidence, how much they stick together … I wanted to put it on Facebook and go viral so that the people could see,” she told the Los Angeles Times.