Omar Mateen, the U.S.-born man responsible for the deadliest mass shooting by a single gunman in the country's history, was a chameleon — a devoted father to some, an angry bigot to others.

Authorities say 49 people are dead and 53 others wounded after Mateen opened fire with an assault rifle inside the Pulse nightclub in Orlando, Fla., early Sunday. He was killed by police.

Noor and Omar Mateen

Noor Salman and Omar Mateen are shown in an undated photo. (Facebook)

Mateen's motives are murky. His father speculated he was angry after seeing two men kiss, but Pulse patrons have told The Canadian Press and other news organizations he was a repeat customer at the club. Mateen claimed to support various Islamic extremist groups, but didn't seem to know much about them, including which ones were in conflict with each other.

Here's what we know about Mateen, 29.

He was born in New York and went to high school in Stuart, Fla. A classmate described him as a typical teenager who played football.

The imam at the mosque Mateen attended for nearly 10 years described him as a soft-spoken regular worshipper who rarely interacted with the congregation.

"He hardly had any friends," Syed Shafeeq Rahman, who heads the Islamic Center of Fort Pierce, told Reuters.

Fellow worshippers at the mosque told the CBC's Susan Ormiston that he last visited the mosque Friday night. One said he seemed like a devoted father, often kissing and hugging his young son.

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Mateen lived what seemed like a quiet domestic life in a ground-floor condo beside a duck pond. Ormiston reported that through the condo's sliding doors one could see a typical living room with an overstuffed leather sofa and walls decorated with dozens of family photos. 

Still, there were worrying signs from people who had spent time with Mateen.

'Not a stable person'

He was married in March 2009 to a woman he met online who moved to Florida to be with him, according to the Washington Post. They were divorced in 2011. The woman said Mateen was "not a stable person" and that he beat her.

Sitora Yusufiy, the ex-wife, told reporters later Sunday he had a violent temper and was emotionally and mentally disturbed, Reuters reported. She also said she was "rescued" from the marriage after four months. 

The woman claimed Mateen wanted to be a police officer and had applied to the police academy.

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Security firm G4S, based in Jupiter, Fla., confirmed in a statement to multiple media outlets that Mateen was an employee of the company since September 2007.

Mateen worked as a security guard for G4S inside the St. Lucie County Courthouse in Fort Pierce. He checked citizens for weapons and sharp objects as they entered through security screening.

A local resident, JayJay Quartino, recognized Mateen from photographs on TV. He told CBC News Mateen was pleasant and even cracked jokes.

But another co-worker, Daniel Gilroy, said Mateen had a violent nature.

"He was an angry person and a bigot," Gilroy said. "He would hit things, and this wasn't seldom, this was almost all the time."

Known to the FBI 

Mateen came to the attention of the FBI in 2013 "when he made inflammatory comments to co-workers alleging possible terrorist ties," Special Agent Ron Hopper said at a news conference Sunday. Authorities interviewed Mateen twice.

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"Ultimately, we were unable to verify the substance of his comments, and the investigation was closed," Hopper said. The FBI investigated him again in 2014 "because of possible ties to an American suicide bomber." Mateen was not currently under investigation or under surveillance.

The FBI says now that Mateen was clearly "radicalized," at least in part via the internet, but there's no evidence he was in contact with any terrorist groups.

Mateen's grasp of the differences between Islamic extremist groups appeared to be shaky. During three calls with 911 dispatchers, Mateen not only professed allegiance to ISIS but also expressed solidarity with a suicide bomber from the Nusra Front, and a few years ago he claimed connections to Hezbollah, too. Both of the latter groups are enemies of ISIS.

Mateen was armed with a handgun and an AR15-type rifle, according to Orlando police. He legally purchased the weapons in Florida within the last week.

May have been a club regular

Mateen's father, Seddique Mir Mateen, told NBC News the attack had nothing to do with religion. He said his son got angry when he recently saw two men kissing in Miami — in front of his own son — and speculated that might have played a part.

However, two regulars of Pulse told The Canadian Press they had seen Mateen partying at the club repeatedly.

Ty Smith and Chris Callen expressed incredulity at the story being told by Mateen's father.

They say Mateen saw plenty of men kiss — and far closer to home than Miami.

"That's bullcrap, right there. No offence. That's straight-up crap. He's been around us," Smith said Monday in an interview at the GLBT Community Center of Central Florida.

"Some of those people did a little more than [kiss] outside the bar.… He was partying with the people who supposedly drove him to do this?"

Smith said the sometime visitor would show up with a buddy and let loose in a way he couldn't when he was closer to the family home: "[He'd get] really, really drunk.… He couldn't drink when he was at home — around his wife, or family. His father was really strict.… He used to bitch about it."​

Corrections

  • A previous version of this story incorrectly stated that Omar Mateen was from Port St. Lucie, Fla. In fact, Mateen lived in Fort Pierce, Fla.
    Jun 12, 2016 8:21 PM ET
With files from Susan Ormiston, Reuters and The Canadian Press