Officials say 50 people were killed at an Orlando, Florida, nightclub early Sunday morning, marking the deadliest mass shooting in modern United States history.
Police initially said "approximately 20 people" were killed in the incident at Pulse, a popular gay nightclub, but raised the number of casualties at a news conference later Sunday morning.
Fifty-three people were taken to local hospitals, police said.
The gunman, who was killed in a shootout with SWAT team members, had an assault rifle, handgun and "some kind of device on him," Orlando Police Chief John Mina said, adding,"It appears he was organized and well-prepared," according to CNN.
The incident is being investigated as an act of terrorism, NBC News says. FBI officials identified the shooter as 29-year-old Omar Mateen at a news conference Sunday afternoon.
The FBI had interviewed Mateen twice after he made suspicious remarks. He was not under current investigation by the FBI.
Mateen's father told NBC News the shooting had "nothing to do with religion" – his son was angry when he saw two men kissing a few months ago, and thinks that may be related to the shooting.
President Barack Obama said in a televised statement Sunday that "we know enough to say this was an act of terror and an act of hate."
The FBI is working with the Orlando Police Department to investigate the shooting.
A police officer working at the nightclub responded to shots fired around 2 a.m. – the officer then exchanged fire with the gunman, ABC News says.
The gunman then went inside the club and took hostages. There were more than 300 people inside at the time of the incident, according to The Associated Press.
Around 5 a.m., a SWAT team went in and rescued the hostages, and the gunman was eventually killed in a gunfight with those officers, ABC News says.
An officer was also shot during the incident, but his kevlar helmet saved him, Mina said.
MN to honor Pulse victims
Minnesotans and others have responded to the shooting.