What We Know About ISIS-K, Alleged Perpetrators of Moscow Concert Hall Massacre

At least 133 people died in a massacre at a concert hall in Moscow on Friday night in what was the deadliest terror attack on Russian soil in over a decade. Islamic State Khorasan (ISIS-K), a terrorist group based in Afghanistan, claimed responsibility for the carnage. The ISIS branch claimed responsibility for the massacre in a statement posted on affiliated social media channels, although neither the Kremlin nor Russian security services have officially assigned blame for the attack. A U.S. intelligence official, meanwhile, told The Associated Press that U.S. intelligence agencies had confirmed that ISIS was responsible for the attack....