In Orlando massacre, a search for motive and missed signals

A day after America woke to news of a horrific mass shooting at a Florida gay nightclub, a disturbing portrait of 29-year-old gunman Omar Mateen — who was on the FBI’s radar — began to emerge. Director James Comey defended his agents’ multiple investigations of Mateen, whose ex-wife said he was full of hate, and who President Obama called a homegrown extremist. William Brangham reports.