A gunman opened fire at a gay night club in Orlando, Florida, early Sunday, killing 50 people and wounding 53 more before he was killed in a shootout with SWAT team members. Here’s what we know about the deadliest mass shooting in U.S. history: THE SHOOTER: Authorities have identified the shooter as 29-year-old Omar Mateen of Fort Pierce, Florida. In a 911 call from the club, Mateen professed allegiance to the leader of the Islamic State, Abu Bakr al-Baghdadi.