WASHINGTON — Sometime after 2 a.m. Sunday, Omar Mateen dialed Orlando’s 911 service to alert the dispatcher to the carnage unfolding at one of the city’s most popular gay bars. He spelled out his full name and location, and then offered an explanation: He was a follower of the Islamic State.
By 5 a.m., Mateen lay dead, killed in a gun battle with police in a violent finale to the worst mass shooting in US history. But while the horror of the crime was quickly apparent, authorities were just beginning to sort through the jumble of motives behind it.
Mateen, the 29-year-old son of Afghan immigrants, was born in New York and lived in Fort Pierce, Fla. He worked as a security guard and bought his weapons legally.
While Mateen claimed allegiance to Islamic State leader Abu Bakr al-Baghdadi, no evidence had emerged by late Sunday pointing to actual ties to terrorist groups or a significant association with jihadist causes.
And although family members said Mateen had expressed anger about homosexuality, the shooter had no record of hate crimes.
He had twice come under investigation by the FBI — once for comments suggesting an affinity for Islamist groups and a second time for vague connections to another Florida man who traveled to Syria to become a suicide bomber.
Neither inquiry turned up evidence of wrongdoing, and Mateen had a blemish-free record when he applied for a Florida license to carry concealed weapons and again when he legally purchased two firearms — an AR-15 semiautomatic rifle and a handgun — just a few days before the shootings.
Until the past week, Mateen appears to have lived a relatively quiet life, as a security guard and father of a young son who kept a modest two-bedroom condominium in Fort Pierce.
The gunman’s father, Seddique, moved his family to Florida when Mateen was a child. The older Mateen would eventually open a business and attempt to dabble in Afghan politics from afar, starting a YouTube channel in Florida on which he sometimes expressed favorable views about the Taliban.
Seddique Mateen insisted Sunday that his son’s violent deeds had nothing to do with religion.
He said Mateen had become enraged a few months earlier at the sight of a pair of gay men being affectionate with each other.
‘‘We were in downtown Miami, Bayside [Marketplace], people were playing music. And he saw two men kissing each other in front of his wife and kid and he got very angry,’’ the father told NBC News. ‘‘They were kissing each other and touching each other and he said, ‘Look at that. In front of my son they are doing that.’ ”
Mateen spent his youth and young adulthood in Florida, attending high school and then obtaining an associate’s degree in criminal justice from Indian River State College in 2006. He held several jobs as a security guard and appeared to have a fondness for law enforcement. In a series of Myspace photos, Mateen is seen taking selfies wearing New York Police Department shirts.
But there were early signs of emotional trouble and a volatile temper, according to a woman who was briefly married to Mateen.
The woman, who spoke on condition on anonymity, described Mateen as an abusive husband who beat her repeatedly while they were married:
‘‘He was not a stable person. He beat me. He would just come home and start beating me up because the laundry wasn’t finished or something like that.’’
She divorced Mateen in 2011.
Mateen later had a son with another woman, who also appears to have left him.