Mass murders inspired copycats well before the existence of social media platforms, but governments around the world still say the industry must do everything in its power to keep criminals from misusing platforms that let anyone with a smartphone instantaneously connect with an audience of millions.

It was exactly that power that the 28-year-old man police say shot 50 people to death at two New Zealand mosques on March 15 sought to leverage, livestreaming video from one of the attacks and posting an 87-page manifesto. His actions prompted renewed scrutiny of how such platforms can become tools for terrorism, what safeguards are available, and how readily they can be deployed.