His ex-wife said he was unstable and beat her. His father said he spoke openly of his disgust for gay people. A co-worker recalled him as a virulent racist.
Those who knew Omar Mateen, the 29-year-old Florida security guard who carried out the worst mass shooting in American history, described him Sunday as an angry and disagreeable person. But the roots of his rage – and much else about his assault on a gay nightclub in Orlando – remained unclear.
Was the killing of 50 motivated by the homophobia Mateen spewed to his family and co-workers? Or by the allegiance to Islamic State that he professed to a 911 operator the night of the attack? Or by a mental unraveling that drove his wife away after four months of marriage?
And what lay behind his choice of a target: a Latin dance party at a club 130 miles from his home?
President Obama acknowledged the unanswered questions about Mateen at the White House, but noted, "What is clear is that he was a person filled with hatred."
Mateen's outbursts and possible connection to terrorists attracted the attention of the FBI twice in recent years. Agents questioned Mateen, the American-born son of Afghan immigrants, twice in 2013 after being told his co-workers suspected he might be linked to terrorists.
The colleagues reported that Mateen had made frightening claims that he had ties to terror groups, including Al Qaeda, a U.S. law enforcement official said. The Wall Street Journal reported that he also told colleagues he had connections with the brothers responsible for the Boston Marathon bombing.
FBI agents closed the 2013 investigation after they determined that Mateen didn't understand how the groups operated and he told investigators that he had been lying and blustering about his terrorist ties.
"Ultimately we were unable to verify the substance of his comments and the investigation was closed," FBI Assistant Special Agent in Charge Ronald Hopper said.
Agents talked to him again in 2014 after learning he had attended the same mosque as Moner Mohammad Abusalha, a 22-year-old Floridian who joined a branch of Al Qaeda in Syria and killed himself and more than a dozen government soldiers in a truck bombing that year. The FBI conducted an intensive investigation into Abusalha.
The investigation into Mateen's relationship with Abusalha revealed that the two men probably knew each other by sight but were barely acquaintances. Hopper told reporters in Orlando that agents "determined the contact was minimal and did not constitute a substantive relationship or a threat at that time."
The FBI had placed Mateen on the terrorist watchlist during the investigations but removed him after he was cleared, according to law enforcement officials who spoke on the condition of anonymity.
Mateen was born in New York and grew up in Florida. He lived in Fort Pierce, about a 10-minute drive from his parents' home in Port Saint Lucie. Current and former neighbors described the area as ethnically mixed with immigrants from Haiti, Guatemala and the Middle East.
His father, Seddique Mateen, is known in the global Afghan community from a TV show he hosts on a satellite network, Payam-e-Afghan TV, about the national politics of his homeland and the ongoing conflict with Pakistan. In one clip from the program, "Durand Jirga," posted online last year, the elder Mateen called the Taliban "our warrior brothers" in opposing Pakistan.
The network owner, Omar Khatab, said the father flew from Florida to California every three months to film broadcasts at the channel's Canoga Park studio and expressed little interest in Islam.
"He is not a religious guy. He's a secular guy," Khatab said. "He loves America. He has been here a long time. He was a nice guy. The son, I don't know about."
Mateen's father told NBC News that the family was not aware he was planning an attack.
"We are in shock, like the whole country," Seddique Mateen said.
Omar Mateen met Sitora Yusufiy, the daughter of Uzbek immigrants, online and married her in 2009, but the marriage was short-lived.
"After a few months he started abusing me physically, very often, not allowing me to speak to my family," Yusufiy said at a news conference in Boulder, Colo., where she lives. She said that her parents rescued her after four months and that she and Mateen eventually divorced.
As their marriage devolved, she said, she grew to believe he was mentally ill.
"He was obviously disturbed," she said.
People who knew him said he had a young son, but the age of the child and Mateen's relationship with the mother was unknown.
Mateen was employed since 2007 as a security guard for the international firm G4S, which provides services to corporations, celebrities and foreign governments. Daniel Gilroy, who worked alongside Mateen for about a year as a security guard for a gated community, said he brought a prayer rug and skullcap to work and prayed on his knees during his shifts.
He didn't talk about his faith, Gilroy said, but was outspoken in his disdain for African Americans, gays and women, frequently using slurs and sometimes talking about committing violence against them. Once, when he saw an African American man driving past, Gilroy recalled, Mateen said he wished he could "kill all" blacks, referring to them with the N-word.
"You meet bigots," Gilroy said, "But he was above and beyond. He was always angry, swearing, just angry at the world."
Gilroy said that he complained, but that the company did not intervene. Representatives from G4S did not immediately return requests for comment about Gilroy's remarks. In a statement earlier in the day, the company said, "We are cooperating fully with all law enforcement authorities, including the FBI, as they conduct their investigation."
The company said Mateen underwent company screening and a background check in 2007 and repeated the process in 2013, with no problems. The company was aware of the FBI inquiry.
Mateen attended the Islamic Center of Fort Pierce, a small mosque with about 150 worshipers, several times a week. Just last Friday, he prayed with his young son. But the center's imam said he did not really know him.
"He was a quiet, shy guy," Imam Syed Shafeeq Rahman said. "Come last, go first."
The imam said he hadn't had a conversation with Mateen in a decade and couldn't reconcile his actions with the teachings of Islam. "In the mosque, there is no extremism," he said.
Mateen's father told NBC News that he believed homophobia, not religion, led his son to kill. The father recalled a visit to Miami earlier this year where his son became angry with displays of affection by gay men.
"We were in downtown Miami, Bayside, people were playing music. And he saw two men kissing each other," Seddique Mateen said. "And then we were in the men's bathroom and men were kissing each other."
Omar Mateen bought two guns he used in the rampage, an assault-type rifle and a semiautomatic pistol, legally in the last two weeks at a gun store near his home, federal officials said.
Near the time he opened fire in the nightclub, Mateen placed a call to 911 and told the operator that he pledged allegiance to Islamic state and specifically mentioned the Tsarnaev brothers, who were responsible for the Boston Marathon bombing, two U.S. law enforcement officials said.
In a live broadcast Sunday afternoon on Payam-e-Afghan, the network that aired Mateen's father's show, an unidentified man speaking in English expressed dismay at the attacks.
"It's not the work of all Afghans. It's not the work of all Muslims," he said. "We are so sad this happened especially for those defenseless people gathering in a nightclub pursuing the happiness they wanted to obtain."
His ex-wife had not talked to Mateen for seven years and, reflecting on their time together, said he practiced his faith and showed no signs of interest in radical Islam. He talked about becoming a police officer. But then there was his temper.
"When he would get in his tempers, he would express hate toward everything," she said.
Ryan reported from Los Angeles, Wilber from Washington and Jarvie from Fort Pierce, Fla.
5:36 p.m.: This article was updated with additional details and comments from Sitora Yusufiy and Daniel Gilroy.