A complicated picture has emerged of 29-year-old Omar Mateen, who opened fire in a gay Orlando nightclub. The attack left 49 dead and dozens more wounded in the worst mass shooting in modern U.S. history.

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CONFLICT WITH SEXUALITY?

While many have condemned the attack at the Pulse nightclub as a hate crime against the gay community, and his own father suggested Mateen may have acted out of anti-gay hatred, reports have surfaced that Mateen himself was a regular there.

"He was trying to pick up people. Men," Jim Van Horn, 71, told The Associated Press. "He would walk up to them and then he would maybe put his arm around them or something and maybe try to get them to dance a little bit or something. And then go over and buy a drink or something. That's what people do at gay bars, you know? That's what we do."

The Orlando Sentinel and other news organizations quoted other Pulse regulars who said they had seen Mateen there a number of times.

"Sometimes he would go over in the corner and sit and drink by himself, and other times he would get so drunk he was loud and belligerent," Ty Smith said.

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BORN IN AMERICA

The son of Afghan immigrants, Mateen spent most of his childhood on Florida's Atlantic coast and lived there as an adult, not far from his parents. Born in the New York City borough of Queens in 1986, he moved with his family to the Long Island town of Westbury two years later and then in 1991 to Port Saint Lucie, Florida, about 125 miles southeast of Orlando.

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STRING OF JOBS

Like many young men, Mateen worked a series of unremarkable jobs after high school. He eventually found stability with a security guard job in South Florida. He still held that when he attacked the nightclub and was killed by police.

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CO-WORKER TENSION?

A one-time co-worker with security company G4S remembered Mateen as an angry man who used slurs for gay people, blacks, Jews and women, and threatened violence.

Daniel Gilroy said Mateen badgered him and sending him dozens of text messages daily, and that he reported Mateen's behavior to his bosses.

"I kind of feel a little guilty that I didn't fight harder," Gilroy said. "If I didn't walk away and I fought, then maybe 50 people would still be alive today."

Gilroy told The New York Times that Mateen "talked about killing people all the time." Of the massacre, Gilroy said, "I saw it coming."

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UNSUCCESSFUL MARRIAGE

An early marriage faltered. Mateen's ex-wife, Sitora Yusufiy, told reporters she believed he suffered from mental illness. Although records show the couple didn't divorce for two years after their 2009 marriage, Yusiufiy said she was with Mateen for only four months because he was abusive. She said he would not let her speak to her family and family members had to come literally pull her out of his arms.

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MARRIED AGAIN

It's unclear when Mateen married his second wife, Noor Salman, but an Aug. 30, 2013, property deed in Saint Lucie County identified them as a married couple. Family members said the pair had a young son about 3 years old.

FBI Director James Comey said the agency was trying to determine whether Mateen had recently scouted Disney World as a potential target, as reported by People.com, which cited an unidentified federal law enforcement source. The report said he visited with his wife.

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FBI SCRUTINY

The FBI became aware of Mateen in 2013 when co-workers reported that he claimed to have family connections to al-Qaida and to be a member of Hezbollah, too, FBI Director James Comey said. The agency conducted a 10-month preliminary investigation, following Mateen, reviewing his communications and questioning him, the FBI chief said. Mateen claimed he made the remarks in anger because co-workers were teasing him and discriminating against him as a Muslim. The FBI eventually closed the case, Comey said.

His name surfaced again as part of another investigation into a suicide bomber from the Syrian rebel group Nusra Front. The FBI found Mateen and the man had attended the same mosque and knew each other casually, but the investigation turned up "no ties of any consequence," Comey said.

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HIS GUNS

Mateen bought at least two firearms legally within a week or so before the attack, according to Trevor Velinor of the Bureau of Alcohol, Tobacco and Firearms.

He bought them at the St. Lucie Shooting Center. Store owner Ed Henson said Mateen passed a full background check and that if he hadn't bought the guns there, he would've gone somewhere else. Henson said he's sorry this "evil person" bought the guns from his business.