Omar Mateen of Port Lucie, Florida has been identified as the suspect.
Omar Mateen, the man police say is behind the deadliest mass shooting in the history of the United States, was a licensed security guard and permitted – despite two recent probes by the FBI into potential ties to radical Islam and terrorism – to carry a gun.
Mr. Mateen, 29, was a security guard with G4S, one of the largest private security contractors in the world, a job that required him to obtain two Florida licences: one to work as a security officer and one to carry a firearm. Public records do not show when he first obtained those licences, but G4S said in a statement that he had been an employee since 2007.
During his nine years with the company, he was twice on the radar of the FBI: In 2013, investigators began scrutinizing him after he "made inflammatory comments to co-workers alleging possible terrorist ties," Ronald Hopper, an assistant agent in charge of the FBI's Tampa office, said on Sunday; in 2014, the FBI became aware of contact between Mr. Mateen and a Florida man who later was a suicide bomber in Syria. The FBI concluded that the relationship between the men was insignificant and that Mr. Mateen "did not constitute a substantive threat at that time," Mr. Hopper said.
Applicants for such licences are screened not only for criminal records, but for arrest records – and must not "have demonstrated a lack of respect for the laws of [Florida] and the nation." Officials with the Florida regulator that performs these checks could not be reached for comment on Sunday.
But based on what little evidence has emerged about Mr. Mateen's life, it is not surprising investigators were uncertain exactly where his loyalties lie.
Although Mr. Mateen reportedly pledged his allegiance to the Islamic State in a 911 call the night of the shooting, one neighbour told a Florida news reporter his car had bumper stickers promoting the U.S. military, including one with the motto of the Marine Corps, Semper Fi, which means "Always Faithful." In photographs that Mr. Mateen posted on the Internet of himself, he wears shirts emblazoned with the logo of the New York Police Department – the law enforcement agency that was celebrated for its response to the terrorist attacks of Sept. 11, 2001. In a news conference on Sunday night, Mr. Mateen's former spouse said that he aspired to be a police officer, but was emotionally and mentally disturbed, with a tendency to turn violent.
Sitora Yusufiy told reporters she was "rescued" by family members from her ex-husband after four months of a stormy marriage that ended in divorce.
Mr. Mateen's family appears to have little to do with the brand of radical Islam that has motivated terrorist attacks in Paris, Belgium and California – a point on which Mr. Mateen's father was adamant during a brief interview with NBC News on Sunday.
"This has nothing to do with religion," Seddique Mir Mateen told the network. One of the few clues that Seddique Mateen was able to offer the network about what might have motivated his son came in the form of an anecdote from a recent trip they took to Miami. He said his son became "angry" when he noticed two men being affectionate. "They were kissing each other and touching each other, and he said, 'Look at that. In front of my son they are doing that.' And then we were in the men's bathroom and men were kissing each other," Seddique Mateen said.
The elder Mr. Mateen, who was born in Afghanistan, was host of a self-produced television show called Durand Jirga, which was dedicated to discussing the Durand Line, a disputed boundary between Afghanistan and Pakistan.
Omar Khatab, owner of the California-based satellite channel Payam-E-Afghan, which broadcast the show, met with Mr. Mateen's father on multiple occasions. "[Seddique Mateen] was a secular kind of person. He was not a fanatic or religious," Mr. Khatab told The Globe and Mail. "He was not politically radicalized or a hard-core Muslim."
He said Mr. Mateen's father had not shown up for any recordings in almost a year, and that he had no contact with any other members of the family.
It is not clear when the Mateens settled in Florida. Public records show Omar Mateen was born in New York, but he and his father own homes near each other on Florida's east coast.
Media reports said Omar Mateen had worked at both a juvenile detention facility that was run by private contractors and a gated community.
One former peer told the Orlando Sentinel Mr. Mateen was an outsider in his high school years and was the target of bullying.
"You could tell it hurt his feelings," Brice Miller said, "but he would laugh it off."
"He was just dorky," Mr. Miller said. "He was disliked, but he always tried to get you to laugh."