The massacre is the worst mass shooting in United States history. Mateen has been identified as the gunman who killed 50 people and injured 53 others when he opened fire inside Pulse Nightclub, a crowded Florida gay nightclub, early Sunday morning. Names of victims are starting to be released.So-called Islamic State has claimed responsibility for the attack.President Barack Obama said shooter was ‘filled with hatred’.Governor Rick Scott declares a state of emergency in Florida.Send this page to someone via email email.