Omar Mateen: Gunman who killed 50 in Orlando gay club Pulse identified by police

Authorities confirm identity of killer as his father says 'this has nothing to do with religion'

(EPA/Univision)

Police have identified the gunman in the mass shooting at a gay club in Florida as 29-year-old Omar Mateen, an American citizen whose parents are from Afghanistan.

Authorities in Orlando said they were investigating the shooting as an act of terrorism, as the death toll rose to 50 with a further 53 wounded.

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The gunman was killed in a shootout with armed officers at around 5am on Sunday morning, US time. He was armed with an assault-type rifle, a handgun and some sort of "suspicious device", police said.

CBS News initially identified the suspect as Mateen, a US citizen with no apparent criminal record. ABC News reported he had been on police's "radar", though not subject to an investigation.

And according to The Washington Post, relatives helped officials identify Mateen as the shooter. He lived in Fort Pierce, Florida.

Mateen's father, Mir Seddique, told NBC News his son had become angry a couple of months ago when he saw two men kissing in Miami, and he believed that could be related to the shooting.

He said the incident "has nothing to do with religion".

"We are saying we are apologizing for the whole incident. We weren't aware of any action he is taking. We are in shock like the whole country," Seddique said.

Orlando police chief John Mina said the suspect exchanged gunfire with an officer working at the Pulse club at around 2am, before going inside and taking hostages among the more than 300 people at the club.

At a press conference, police declared a state of emergency in the city and urged anyone who went to Pulse on Saturday night to come forward and speak to police.

Ron Hopper, the FBI agent in charge of the operation, when asked if the gunman had a connection to radical Islamic terrorism, Hopper said authorities "have suggestions that individual has leanings towards that".

"This is an incident, as I see it, that we certainly classify as domestic terror incident," Orange County Sheriff Jerry Demings said.

Barack Obama was briefed on the attack and has asked for regular updates on the investigation, the White House said.

Pulse posted on its own Facebook page around 2 a.m.: "Everyone get out of pulse and keep running." Just before 6 a.m., the club posted an update: "As soon as we have any information, we will update everyone. Please keep everyone in your prayers as we work through this tragic event. Thank you for your thoughts and love."

The club was opened in 2004 and worked actively in the community to promote awareness of LGBT issues. The Pulse website described it as "not just another gay club".

Mateen is understood to have worked as a security guard and driven to Orlando to carry out the attack, according to CNN.