After calling 911 and pledging allegiance to the Islamic State.
“Fifty dead in Orlando gay nightclub shooting, worst mass killing in U.S. history; gunman reportedly pledged allegiance to Islamic State,” by Matt Pearce and Del Quentin Wilber, Los Angeles Times, June 12, 2016:
A heavily armed gunman who had reportedly pledged allegiance to Islamic State stormed into a packed gay nightclub in Orlando, Fla., early Sunday, and began rapidly firing into the crowd, killing at least 50 people and wounding 53 in the worst mass shooting in U.S. history.
The gunman was killed by a SWAT team after taking hostages at Pulse, a popular gay club, investigators said at an early morning news conference. He has been preliminarily identified as 29-year-old Omar Mateen of Port St. Lucie, Fla., a U.S. law enforcement official said.
Mateen called 911 moments before the attack, pledging allegiance to the Islamic state, a federal law enforcement official said, confirming earlier reports. Federal investigators said they also were looking into reports that he recited prayers to Allah during the attack….