By: Andy Campbell
Officials have identified Omar Mateen as the shooter who killed 50 people and left at least 53 injured at a gay club in Orlando, Florida, on Sunday.
Mateen, an American citizen in his 20s, acted alone and "very quickly" when he opened fire with what officials described as an assault rifle.
Prior to the killings, Mateen called 911 to pledge his allegiance to ISIS. He gave his full name to the operator, and mentioned the Boston Bombers, according to multiple sources who spoke to law enforcement.
He's believed to have acted alone. City officials said he was an American citizen, but noted that many of his family members are not.
Authorities say Mateen attacked the downtown Pulse nightclub at around 2 a.m. He was killed by police following an hourslong hostage situation.