By now, the details of what has become the deadliest mass shooting in U.S. history are well known. A man named Omar Mateen, armed with two firearms and apparently possessed by a loyalty to the Islamic State, killed 49 people as they danced in a club in Orlando, Florida. He injured at least another 50 before the police shot him — fatally — in the ensuing standoff. News agencies have done a decent job of answering the questions that naturally arise when the Islamic State is invoked prior to a mass murder. It wasn't so long ago that similar questions were raised after the shootings in San Bernardino, Calif. If the U.S. government knows the Islamic State is dangerous — which it does — how could someone ostensibly affiliated with the group go unnoticed? How far is the Islamic State's reach?