Who is Omar Mateen, the Orlando nightclub shooting gunman?

ORLANDO — The gunman who committed a mass shooting at Pulse nightclub in Orlando, Florida has been identified by the FBI as Omar Saddiqui Mateen.

Suspect identified as Omar Mateen, 29. An American citizen born in New York. <a href="https://twitter.com/FBI">@FBI</a> first became aware of him in 2013 <a href="https://t.co/gt18lhTM4G">pic.twitter.com/gt18lhTM4G</a>

NBC is reporting that Mateen called 911 and declared allegiance to ISIS before the attacks, but this has not been confirmed by law enforcement.

BREAKING: Before Orlando club shooting, gunman called 911, swore allegiance to ISIS - law enforcement sources to NBC <a href="https://t.co/PhLHUG75j1">https://t.co/PhLHUG75j1</a>

Islamic State claims responsibility for Orlando nightclub shooting <a href="https://t.co/BrBr7fTIKt">https://t.co/BrBr7fTIKt</a>

We can confirm the shooter as Omar Mateen of Port St. Lucie <a href="https://twitter.com/hashtag/wftv?src=hash">#wftv</a> <a href="https://twitter.com/WFTV">@wftv</a>

Mateen is reportedly a U.S. citizen from Fort Pierce, Florida and is not believed to have had a criminal record. WFTV is reporting that law enforcement was aware of Mateen before the nightclub shooting, but was not the target of any active investigation.

CNN is reporting that Mateen, 29, worked as a private security guard. His employer confirmed that information Sunday afternoon.

Statement from G4S, security company that employed <a href="https://twitter.com/hashtag/OrlandoShooting?src=hash">#OrlandoShooting</a> suspect Omar Mateen <a href="https://t.co/9BnigdmyZK">pic.twitter.com/9BnigdmyZK</a>

Mateen's parents are from Afghanistan, according to CBS.

Approximately 50 people were killed and over 50 injured in the attack on the gay nightclub that happened early Sunday morning. The gunman, officially identified as Mateen, is also dead. The attack is the worst mass shooting in U.S. history.

This is a developing news story, visit