It has been a horrific few days since Stephen Paddock committed the worst mass shooting in modern U.S. history at the Mandalay Bay Resort and Casino on Sunday night. But when the Islamic State (ISIS) claimed the attack just hours after it had taken place, the tragedy took on a strange new dimension. How could Paddock, a 64 year old man with no criminal history or known radical beliefs, and whose crime police had not initially investigated as a terrorist attack, have acted on behalf of ISIS?