[Update] 50 People Killed At Gay Nightclub In Orlando In "Domestic Terror Incident"

JUST IN: Florida gov. declares State of Emergency in aftermath of Orlando mass shooting https://t.co/ZdaJMt338S pic.twitter.com/70yvflfVkd

Mateen's father, Mir Seddique, told NBC News that the incident "has nothing to do with religion," and stemmed instead from an incident a few months ago when his son "saw two men kissing in Miami" and became enraged. He added, "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."

The Daily Beast reports that Mateen has previously been investigated for possible terror links:

The senior law enforcement source reports that Mateen became a person of interest in 2013 and again in 2014. The Federal Bureau of Investigation at one point opened an investigation on Mateen but subsequently closed the case when it produced nothing that appeared to warrant further investigation.

“He’s a known quantity,” the source said. “He’s been on the radar before."

The gunman is said by the source to have been born in New York and to have been married for a time to a woman from New Jersey. His father, Seddique Mateen, appears to reside in Florida, but is said to be presently running for office in Afghanistan.

There will be a vigil in front of Stonewall Inn on Monday night: "Please join us on Monday, June 13 at 6PM outside of the Stonewall Inn as we remember the lives lost to such senseless violence and stand together against these acts."

There have been at least 892 mass shootings in America since Sandy Hook in December 2012.

[Original Story Below] At least 20 people were killed and 42 others were seriously injured when a gunman opened fire at a gay nightclub in Orlando, Florida last night. The gunman was fatally shot by police after a standoff, and according to the Times, cops have classified the attack as a “terror incident.”

Orange County Sheriff Jerry Demings said investigators are looking into whether this was an act of domestic or international terror: "This is an incident, as I see it, that we certainly classify as domestic terror incident."

"It's appears he was organized and well-prepared," Orlando Police Chief John Mina said during a press briefing this morning, adding that the shooter had started around 2 a.m. at nightclub Pulse, which describes itself as "the hottest gay bar" in Orlando. An officer who was working at the club engaged in a shootout outside the club, after which the gunman ran inside and started taking hostages.

There were approximately 320 people in the club at that time. "The shooter took hostages and at about 5 a.m. we entered and exchanged gunfire with the suspect and he was dead at the scene," Mina said, adding police used a "controlled explosion" at one point to distract the shooter. "Nine officers were involved and one of our officers was injured. At least 30 people were saved during the rescue."

Anthony Torres, who was partying inside the club before the shootings started, posted his account of what happened on Facebook: "People where screaming and running, looking for their loved ones along with seeing injured people sitting on the floor .. It was so surreal,” he wrote. "They are just pulling people out in stretchers loading them up.. Omg please god let everyone make it - tonight was supposed to be a fun night!! One more minute and we would of been shot or worse.. Thank god we got to our car in time,” he said.

Around 3 a.m., Pulse Orlando posted on its Facebook page: “Everyone get out of pulse and keep running." Just before 6 a.m., the club added 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."

CBS News reports, "Sources have confirmed to CBS News that authorities are investigating whether the suspect, who has been named as Omar Mateen, had ties to Islamic terrorism. Mateen is a U.S. citizen with no apparent criminal history, according to sources."

This morning, the White House released a statement, "The President was briefed this morning by Lisa Monaco, Assistant to the President for Homeland Security and Counterterrorism, on the tragic shooting in Orlando, Florida. Our thoughts and prayers are with the families and loved ones of the victims. The President asked to receive regular updates as the FBI, and other federal officials, work with the Orlando Police to gather more information, and directed that the federal government provide any assistance necessary to pursue the investigation and support the community."

Orlando police officers seen outside of Pulse nightclub after a fatal shooting and hostage situation on June 12, 2016 in Orlando, Florida (Getty Images)