Why Facebook didn’t block live video of New Zealand shooting

Why did Facebook air live video of the New Zealand mosque shooting for 17 minutes? Didn’t anyone alert the company while it was happening?

Facebook says no. According to its deputy general counsel, Chris Sonderby, none of the 200 or so people who watched the live video flagged it to moderators. In a Tuesday blog post, Mr. Sonderby said the first user report didn’t come until 12 minutes after the broadcast ended.

All of which raises additional questions among them, why so many people watched without saying anything, whether Facebook relies too much on outsiders and machines to report trouble, and whether users and law enforcement officials even know how to reach Facebook with concerns about what they’re seeing on the service.