What we know about ISIS-K, the group that US officials say is behind the Moscow attack

Russian President Vladimir Putin has said that “radical Islamists” orchestrated the attack in Moscow last Friday that claimed at least 137 lives. But ISIS has claimed responsibility and, more specifically, US officials say ISIS-K was behind the violence. The World’s host Marco Werman spoke with Michael Kugelman, the director of the South Asia Institute at the Wilson Center, who says ISIS and its offshoot in Afghanistan view Russia as a “crusader state.”