Omar Mateen: Who was the gunman responsible for the Orlando gay nightclub massacre?

Here's what we know about Omar Mateen, the US-born extremist who murdered 50 people in a gay nightclub.

  • Islamic State allegiance?

Omar Mateen took a host of selfies and posted them on social media. Credit: Reuters

Mateen, 29, pledged allegiance to so-called Islamic State's leader Abu Bakr al-Baghdadi in a phone call to 911 just moments before he launched the attack.

The group said an IS "fighter" carried out the attack but the extent of its involvement in the planning and execution is unknown.

  • FBI interviews

The 29-year-old was known to the FBI. Credit: Reuters

Mateen was on the FBI's radar over his possible links to terrorism.

He was questioned twice in 2013 after making "inflammatory" comments to a colleague about Islamist extremism.

The next year, he was investigated again over his ties with an American who fled to Syria to become a suicide bomber.

But FBI agents took no further action and closed the case.

He was able to legally purchase firearms used in the attack last week.

  • Father says attack had nothing to do with religion

Fifty people were murdered at Pulse nightclub. Credit: Reuters

Mateen's father told NBC News the attack had "nothing to do with religion".

He said his son was enraged when he saw two men kissing in front of his family.

He said his family were completely unaware what Mateen was planning, saying they "are in shock like the whole country".

"We are apologising for the whole incident," he said.

  • Ex-wife abuse claims

Omar Mateen seen in one of many photos from his social media accounts. Credit: Reuters

His ex-wife said Mateen was violent, mentally unstable and regularly beat her during their eight years of marriage.

Sitora Yusufiy told reporters she was "devastated, shocked, started shaking and crying" when she heard that her former husband was responsible for the atrocity.

She described him as a "mentally ill" individual who frequently used steroids.

Yusufiy said her family had to "rescue her" from her violent husband and had to physically pull her out of his arms.

She also revealed that Mateen wanted to become a police officer and applied to a police academy.

They officially divorced in 2011.

  • Born in New York to Afghan parents

Mateen was born in the US. Credit: Reuters

Mateen was born in New York to Afghan parents but moved to Fort Pierce, a city around 120 miles away from the nightclub where he carried out the massacre.

A gay high school classmate described him as a typical teenager who showed no signs of being homophobic.

"He did not show any hatred to any of us," he told Reuters. "He treated us all like the individuals we were. He always smiled and said hello.”

The imam of a Florida mosque that Mateen attended for nearly 10 years said he was a softly-spoken man who visited regularly but would never interact with the rest of the congregation.

"He hardly had any friends."

Mateen had worked for security company G4S since 2007 as a guard for a gated retirement community in South Florida.

He carried a gun as part of his duties and hadpassed background security checks twice, the latest in 2013, the company said.