The gunman who opened fire at a gay nightclub in Orlando, Florida, killing 49 people early Sunday morning was born in New York, law enforcement sources told NBC News.
Omar Mateen, 29, was born in 1986 and moved to Florida as a young child. He was listed as living at a residence in Port St. Lucie, about 125 miles south of Orlando, law enforcement sources said.
Mateen's father told NBC News, "this has nothing to do with religion." Mir Seddique said his son got angry when he saw two men kissing in Miami a couple of months ago and thinks that may be related to the shooting.
"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," Seddique said.
Seddique also said Mateen was a husband and father to a 3-year-old boy.
A man who picked up the phone at Mateen's listed address, Mustafa Abasin, told NBC News: "We are in shock and we are sad." He would not explain how he knew the gunman, but added that he was aiding investigators.
Law enforcement sources told NBC News just before the attack began, the shooter called 911 and swore allegiance to ISIS.
Rep. Alan Grayson, a Democrat from Florida whose district includes the site of the shooting, suggested to reporters that "more likely than not" the massacre was ideologically motivated.
"Let me put it this way," Grayson said, "the nationality of family members is indicative."
The family's background was not immediately clear, but Grayson said Mateen was a U.S. citizen.
The New York City Police Department said in a statement they are in contact with law enforcement authorities in Florida and the FBI as they closely monitor developments. “Meanwhile, the NYPD has placed our Patrol and Counter-terrorism resources, including CRC, SRG and ESU personnel, on alert pending further information."
Officials previously said a gunman opened fire at Pulse Nightclub in Orlando around 2 a.m. A uniformed officer working at the nightclub exchanged gunfire with the shooter, who was armed with an assault-type rifle, a handgun and a suspicious device.
"The officer engaged in a gun battle with that suspect. The suspect at some point went back inside the club and more shots were fired. This did turn into a hostage situation," Orlando Police Chief John Mina said during a news conference said.
The gunman was shot dead when a SWAT team entered the club, police said.
With at least 49 killed, the massacre is the deadliest mass shooting in the history of the United States. It comes amid national celebrations marking LGBT pride month.
"Our hearts break for the victims and families of this horrific act of violence. We stand in solidarity with the LGBTQ community in #Orlando," GLAAD tweeted.