While Facebook, Twitter, and Google’s YouTube all took down videos of deadly shooting sprees at two New Zealand mosques, they weren’t fast enough to keep the graphic footage from going viral.

The spread of the footage from attacks that left 49 people dead provides the latest illustration of how digital platforms that enable anyone with a smartphone to instantaneously reach an audience of millions can be wielded by terrorist and hate groups. It’s prompting immediate scrutiny of available safeguards and how readily they can be deployed.