LONDON, UNITED KINGDOM - DECEMBER 05: Police officers and crime scene investigators investigate a crime scene at Leytonstone tube station in east London, England, on December 05, 2015 after a man was seriously injured in a knife attack and it is treated as a terror attack because the attacker reportedly shouted "This is for Syria" during the attack. (Photo by Tolga Akmen/Anadolu Agency/Getty Images)
