Update: 16:24 ET: After the FBI dismissed their 2013 and 2014 interviews with Orlando shooter Omar Mateen as "inconclusive," the Bureau interviewed him again later about his contacts with Moner Mohammad Abusalha, the first US citizen to carry out a suicide bombing in Syria, the AFP has reported. "We determined the contact was minimal and did not constitute a substantive relationship or a threat at that time," FBI Special Agent Ronald Hopper told reporters. In retrospect, it appears to have been more more than just minimal.

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Update 15:50 ET: Accoding to an FBI official, Omar Mateen was acting alone, adding during a press briefing that the investigators are not looking for any second suspect.

. @FBI we do NOT have a second suspect that we are looking for. pic.twitter.com/p6O4TGFfuw — Orlando Police (@OrlandoPolice) June 12, 2016

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Update: 15:34 ET: During a press briefing, an FBI official confirmed that Mateen called 911 and “stated his allegiance to Islamic State.” He added that the FBI first became aware of Mateen in 2013, when he made derogatory and inflammatory comments to his co-workers, alleging possible terrorist ties, an FBI official told journalists during the briefing. The FBI interviewed him twice in 2013 but was unable to verify the substance of his comments. Mateen was then once again questioned by the FBI in 2014 about his possible connections to a known US terrorist suicide bomber, the official said, adding that the questioning revealed that their contacts were minimal and Mateen had not been considered a threat.

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Update 15:30 ET: According to the Orlando Police and federal officials, Mateen legally bought two guns last week, federal officials said. The suspect "purchased a handgun and a long rifle within the last few days," Trevor Velinor, assistant special agent in charge at the ATF Tampa Field Division, told reporters at a briefing.

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Update 13:32 ET: Omar Mateen, who several years ago changed his name from just Omar Mir Seddique and added the Mateen part to his official name, is now said to have pledged allegiance to ISIS. As the Post reports, Omar Mateen had committed himself to ISIS before carrying out the bloodiest mass murder in US history at a gay nightclub in Orlando on Sunday, federal officials said. ateen “made a pledge of allegiance to ISIS,” California Rep. Adam Schiff, the top Democrat on the House Permanent Select Committee on Intelligence, told CNN.

And in an even more surprising update, NBC reports that moments before the shootings, Omar Mateen called 911 to pledge allegiance to ISIS.

Orlando gunman called 911 moments before shooting and pledged allegiance to leader of ISIS, sources tell NBC News https://t.co/0XkMoA2xo2 — NBC News (@NBCNews) June 12, 2016

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Update 13:15 ET: According to WaPo, the ex-wife of the 29-year-old shooting suspect said he was violent and mentally unstable and beat her repeatedly while they were married. The ex-wife said she met Omar Mateen online about eight years ago and decided to move to Florida and marry him. At first, the marriage was normal, she said, but then he became abusive.

“He was not a stable person,” said the ex-wife, who spoke on the condition of anonymity because she feared for her safety in the wake of the mass shooting. “He beat me. He would just come home and start beating me up because the laundry wasn’t finished or something like that.”

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Update 12:55 ET: A picture of the suspected attacker - who was earlier identified as Omar Mateen - has now been published by CBS news.

More pictures:

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Update 12:35 ET: Cited by CNN, Congressman Adam Schiff, the top Democrat on the House Permanent Select Committee on Intelligence, said that Orlando nightclub shooter Omar Mateen "made a pledge of allegiance” to Islamic State and was “heard praying in a foreign language.” Earlier, Senator Bill Nelson also talked about the alleged links between Mateen and Islamic terrorists.

"I asked the FBI if there was any connection to Islamic radicalism. There appears to be. But they are naturally cautious and waiting throughout to see if if this is [in fact true]," Nelson said at a news conference on Sunday.

My full statement on the #Orlando shooting this morning: pic.twitter.com/viERHIljen — Adam Schiff (@RepAdamSchiff) June 12, 2016

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Update 12:25 ET: Mir Seddique, the Afghan immigrant father of the suspected shooter, says it is intolerance of homosexuality, and not affiliations with radical Islam, that likely provoked the attack. "This has nothing to do with religion," he told NBC, stating that he was “in shock like the whole country.” He went on to relate a “recent incident” that demonstrated his son’s attitudes. "We were in Downtown Miami, Bayside, people were playing music. And he saw two men kissing each other in front of his wife and kid and he got very angry. They were kissing each other and touching each other and he said, 'Look at that. In front of my son they are doing that.' And then we were in the men's bathroom and men were kissing each other."

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Update 12:23 ET: The shooting "appears to be connected to Islamic radicalism" according to Florida Senator Ben Nelson

#Orlando shooting "appears to be connected to Islamic radicalism" - Florida Sen Bill Nelsonhttps://t.co/rVSzoSakq0 https://t.co/jdFI52iT8E — BBC Breaking News (@BBCBreaking) June 12, 2016

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Update: 12:10 ET: Take this with a grain of salt (source is CNN), but according to Breaking911, an FBI source reported to CNN that the shooter was known as suspected ISIS sympathizer

BREAKING: FBI Source Reported To CNN That Shooter Was Known As Suspected ISIS Sympathizer - https://t.co/uzG33o5JaH pic.twitter.com/wVyFszpRlQ — Breaking911 (@Breaking911) June 12, 2016

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Update: 12:07 ET: CBS reports that Omar Mateen was on law enforcement radar in last five years,

JUST IN: Omar Mateen was on law enforcement radar in last five years, @jeffpeguescbs reports https://t.co/yjXjCLx2Hm pic.twitter.com/Wm5aamNN4v — CBS News (@CBSNews) June 12, 2016

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Update 11:24 ET: ABC reports that Mateen's parents were born in Afghanistan, and he was "on the radar" of U.S. officials for some time, but was not the target of a specific investigation, law enforcement officials told ABC News.

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Update 11:15 ET: According to the gunman's father, the shooting had nothing to do with religion, and adds that his son got enraged after seeing men kissing recently.

Father of suspect in Orlando massacre tells NBC News his son was enraged after seeing two men kissing recently https://t.co/RrFwArkZqt — NBC News (@NBCNews) June 12, 2016

The suspected gunman in today's gruesome Orlando nightclub shooting which killed at least 50 and injured 53, has been identified by relatives and law enforcement officials as Omar Mateen, a 29-year-old from Fort Pierce, Florida, CBS reports. According to social media, he is a US citizen, born in 1986, from Port Saint Lucie, FL. and both his parents are from Afghanistan. He was a registered democrat with a security officer and firearms license. Florida Congressman Alan Grayson adds that he believes the attack is "more likely than not" ideologically motivated.

NBC's Pete Williams reports that terrorist was on a "watch list" over associations w "suspicious" people several years ago.

The Orlando Mayor said Mateen was armed with a hangdun as well as an AR-15 assault rifle.

CBS added that the FBI is currently checking if he was linked to extremists.

According to BBC, Mateen was not on any terrorism watch list, although as CBS also adds Islamic terrorism is being investigated as one of the possible motives behind the mass shooting.

CNN adds that the suspected Orlando gunman was trained in use of weapons.

Suspect in #Orlando, Omar Mateen is U.S. citizen from Port Saint Lucie, FL. His parents are from Afghanistan. He was born 1986. — Ahmed Shihab-Eldin (@ASE) June 12, 2016

JUST IN: Orlando nightclub shooter ID'd as Omar S. Mateen, law enforcement sources tell @CBSNews https://t.co/zcv0mxzLiR — CBSN (@CBSNLive) June 12, 2016

Some more details on the alleged shooter as disclosed on Find the Data, disclose that he was a registered Democrat in the 18th Congressional District.

A search of the Florida Department of Agriculture and Consumer Services database reveals that Mateen had security officer and firearms licenses: