https://phys.org/news/2019-03-facebook-flagged-nz-mosque-livestream.html

Facebook removed the video "within minutes'" of being notified by police, said Chris Sonderby, Facebook's deputy general counsel.

"No users reported the video during the live broadcast," and it was watched about 4,000 times in total before being taken down, Sonderby said. "We continue to work around the clock to prevent this content from appearing on our site, using a combination of technology and people."