Derrick Miller places flowers at a makeshift memorial outside the Dr. Phillips Center for the Performing Arts, for the mass shooting victims at the Pulse nightclub June 13, 2016 in Orlando, Florida.
The American gunman who launched a murderous assault on a gay nightclub in Orlando was radicalized by Islamist propaganda, officials said Monday, as they grappled with the worst terror attack on US soil since 9/11. The Islamic State group claimed slain shooter Omar Mateen was acting as "one of the soldiers of the caliphate in America" when he attacked the Pulse club in the Florida resort city, an assault that ended when police stormed the venue. 
 / AFP / Brendan Smialowski        (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images)