A gunman killed 50 people at a packed gay nightclub in Orlando, Florida on Sunday and wounded 53 others before being killed by police in the worst mass shooting in U.S. history.
The shooter was identified as Omar Mateen, a Florida resident who a senior FBI official said might have had leanings towards Islamic State militants.
Officials called the rampage a “terrorism incident,” but cautioned that the suspected Islamist connection required further investigation.
Orlando Mayor Buddy Dyer said the attack was the deadliest single U.S. shooting incident, eclipsing the 32 people killed in the 2007 massacre at Virginia Tech University.
“Today we’re dealing with something that we never imagined and is unimaginable,” Dyer said.
He said the casualty doubles an earlier estimate that about 20 bodies were found in the Pulse nightclub.
A police officer working as a security guard inside the club, which has operated in downtown Orlando since 2004, exchanged fire with the suspect at about 2 a.m. (0600 GMT), police officials said.
A hostage situation quickly developed, and three hours later SWAT team officers used armoured cars to storm the club before shooting dead the gunman.
It was unclear when the gunman killed the victims.
Police said one officer was injured after he was hit in his helmet while exchanging fire with the gunman.
“Do we consider this an act of terrorism? Absolutely,” said Danny Banks, special agent in charge of the Florida Department of Law Enforcement.
“Whether that is domestic terrorist activity or an international one that is something we will certainly get to the bottom of,” Banks said.