The journalism of terror: how do we bear witness when everybody is a witness?

In the new reality of terrorism and propaganda on social media, the value of journalism as a means of separating news from noise has never been more vital. With militant groups using social media as a means of propaganda, there are new pressures and ethical challenges for traditional newsrooms. How do journalists engage with the kind of horrific video emerging from groups such as ISIS? How do report on acts of real-time terror such as the Charlie Hebdo massacre? When anyone can witness first-hand on social media unspeakable brutality, what are the responsibilities of those of us in traditional media?