Facebook, Twitter and Google faced scrutiny from U.S. lawmakers on Wednesday over their role in distributing violent and extreme material online.

The hearing comes after two mass shootings earlier this year- in New Zealand and the U.S. state of Texas.

CGTN’s Harry Horton reports.

Andrew Selepak discusses online extremism

CGTN’s Wang Guan spoke with Andrew Selepak, professor and director of the graduate program in Social Media at the University of Florida, about efforts to moderate digital content.