Fifty people have been confirmed dead and dozens of others injured after a gunman opened fire inside a packed gay nightclub in Orlando.
The Washington Post reported that 50 people were killed in what authorities are now describing as a case of domestic terrorism at Pulse, a popular gay club.
The shooter, who police identified as Omar Mateen, 29, was reportedly shot and killed by the police after a shootout.
Though Mr Mateen was born in Florida, his parents are believed to be from Afghanistan.
Police are still trying to identify the possible motive for the killing.
“It appears he was organized and well-prepared,” Orlando Police Chief John Mina said at a Sunday-morning news conference.
Mr. Mina said the shooter had an assault-type weapon and a handgun.
“This is an incident … that we certainly classify as a domestic terror incident,” Orange County Sheriff Jerry Demings said at the news conference. The FBI is involved in the investigation, authorities said.
“We had a crime that will have a lasting effect on our community,” Orlando Mayor Buddy Dyer said. “We need to stand strong, we need to be supportive of the victims and their families.”
The police said though Mr. Mateen was known to authorities he was not under investigation.
The White House said President Barack Obama was briefed on the incident Sunday.
“Our thoughts and prayers are with the families and loved ones of the victims,” the White House said in a statement.
The statement added that Mr. Obama has requested for regular updates.
The Pulse posted a message around 2 a.m. local time on Facebook: “Everyone get out of pulse and keep running.”
There were around 300 people inside the club at the time of the shooting.
A police Swat team arrived within minutes of the shooting and engaged the shooter.
The incident later developed into a hostage situation.
Mr. Mina later told journalists that the man was also armed with “suspicious device” alongside his guns.
There was also a report of a controlled explosion later.
The police said the gunman was killed three hours after the shooting began.