DUSHANBE, June 13, 2016, Asia-Plus – Quoting the FBI, US media outlets report that a gunman who killed 50 people at a gay nightclub in Orlando, Florida early on June 12 called an emergency police-dispatch operator just before the mass killing and swore allegiance to the so-called Islamic State (IS) terrorist group.

The FBI identified the gunman responsible for the deadliest mass shooting in the United States and the nation''s worst terror attack since 9/11 as 29-year-old Omar Mateen, a U.S.-born citizen of Afghan descent.

According to CNN, Mateen carried an assault rifle and a pistol into the packed Pulse club about 2 a.m. Sunday and started shooting, killing 50 people and wounding at least 53.

After a standoff of about three hours, while people trapped inside the club desperately called and messaged friends and relatives, police crashed into the building with an armored vehicle and stun grenades and killed Mateen.

There has been no claim of responsibility for the attack on jihadi forums, but ISIS sympathizers have reacted by praising the attack on pro-Islamic State forums.

“We know enough to say this was an act of terror and act of hate,” President Obama said in an address to the nation from the White House.

Omar Mateen was married in 2009 to a woman originally from Uzbekistan, according to the marriage license, but he filed documents to end the marriage in 2011.

Sitora Yusufi, interviewed by CNN in Boulder, Colorado, said she and Mateen were together about four months, though it took a long time to complete the divorce because they lived in different parts of the country after separating.

Mateen was a normal husband at the beginning of their marriage but started abusing her after a few months, she said.  She said Mateen was bipolar, although he was not formally diagnosed.  She also said Mateen had a history with steroids.  He was religious but she said she doesn''t think his religion played in to the attack.

Reuters report that working for the global security firm G4S during the past nine years, Omar Mateen was an armed guard for a gated retirement community in South Florida, and had cleared two company background screenings, the latest in 2013, according to G4S.

Preliminary investigations reportedly suggested the attack was inspired by Islamic State militants, though there was no immediate evidence that Mateen had any actual ties to the group.

Mateen had twice been interviewed by FBI agents, in 2013 and 2014, after making comments to co-workers indicating he supported militant groups, but neither interview led to evidence of criminal activity, the FBI''s Hopper said.