Orlando: This is where the investigative road divides spectacularly: was Orlando gunman Omar Mateen driven by a love of Islamic State, or by a deep sense of self-loathing – possibly triggered by an awareness that he was gay?

Given that investigators have yet to come up with answers, some might have leapt on the Mateen story earlier than they sensibly should have. In claiming responsibility for Sunday's attack, IS will be acutely embarrassed if the emerging story of Mateen's homosexuality becomes the dominant narrative.

Similarly, Republican presidential nominee Donald Trump's hectoring about global terrorism and Muslim migration will seem misguided if there's nothing to link Mateen to foreign movements and he is confirmed to be a case of what US President Barack Obama has called "the kind of home-grown extremism that all of us have been concerned about".

The ultimate answer might be that a mixture of the two drove the 29-year-old college graduate to perpetrate America's worst gun massacre – 49 dead and 53 people hospitalised, most of them gay and Latino.

For now, the threads to the Mateen story are like spaghetti thrown at a wall. On Monday evening, in the minutes before an emotional vigil for the victims, 56-year-old Dwayne Wesley-Campbell was still perplexed by Mateen's choice of target – Pulse, a gay dance club that Wesley-Campbell and his friends frequented, which was a charnel house when Mateen's three-hour rampage ended in the early hours of Sunday morning.

"I can't figure out what the connection is," Wesley-Campbell says as we await the vigil in the forecourt of Orlando's imposing Dr Phillips Centre for the Performing Arts. "The men kissing each other that [his father says] offended him happened in Miami, not here; and it's a two-hour drive from his home in Fort Pierce to Orlando – why this town and this club?"

Here, then, is the best available version of the life of the slaughterman Mateen, as told by a few investigators and myriad news outlets, based on interviews with his two wives and family, schoolmates and former colleagues and, perhaps most importantly, those who knew him in the central Florida gay community.

Born to immigrant Afghan parents in New York in 1987, Mateen was four years old when the family moved to Port St Lucie, an eastern beachside city in Florida with a population of about 170,000, where accounts of Mateen's school years are contradictory – some say that he was bullied, others that he was the bully.

Threat to bring weapon to school in fifth grade

It was as a pupil at the local Marisopa Elementary School that Mateen first troubled those around him – the teachers and the kids.

Interviewed by the celebrity news website TMZ, former classmate Leslie Hall recalls Mateen as a relentless bully who threw chairs and spat at teachers; and who as early as fifth grade was suspended for two weeks after he threatened to bring a weapon to school, to kill "everyone".

Later, as an early teenager at Martin County High School, classmate Robert Zirkle​ recalls that while they watched real-time TV coverage of the September 11 attacks on New York and Washington, Mateen "stood up in class ... [he was] jumping up and down, cheering on the terrorists".

Zirkle says Mateen became excited, making fun of how America was under attack, and he subsequently made the outlandish claim that Osama bin Laden was his uncle – but Mateen's antecedents were Afghan, whereas bin Laden was Saudi Arabian.

"[Mateen] was making plane noises on the school bus, acting like he was running into a building," Zirkle told The Washington Post. "Before 9/11 happened, we were pretty straight. We all rode the same bus. We weren't really close friends, but friends at least a little," he says, explaining that Mateen took classes in what was called a spectrum alternative school, a campus detached from the main school, which was for students with poor grades or behavioural issues. "After 9/11 happened, he started changing and acting different," Zirkle says.

A crowd gathers for a vigil in honour of the Pulse night club shooting victims in Orlando, Florida. Photo: AP

Other students recall Mateen being sent to the dean's office and suspended for a time. "I remember the kid's dad walking up," one former student tells the Post. "In the courtyard in front of everyone, his dad slapped him right across the face."

Zirkle recalls Mateen as something of a loner. But Christian Cave, also a student at Martin County High School, sees the young Mateen in starkly different terms: "He was cool. I used to see him at house parties ... he made people laugh ... he didn't talk about religion or politics. He must've changed a lot."

Overweight kid who was brutally bullied

Justin Delancy is another who has warm memories of an overweight school kid who was bullied on a bus ride they shared for several years. "He was brutally bullied," Delancy says. "He was a chubby kid and got bullied about his weight."

Confused about Mateen's ethnicity, he adds: "He was probably one of the only kids of Arab descent [and] that made him stand out a bit, as well. On some mornings, kids wouldn't let Mateen sit beside them. On others, he'd get slapped on the back of his head. He'd try to joke and laugh, and make fun of himself to get the attention off of himself. But it didn't work."

Little has surfaced about the circumstances of Mateen's family. An imam in Fort Pierce believes that the father sold insurance; and Sarah Zaidi, a friend of one of Mateen's sisters, says: "[His dad] did stuff with stocks and investment."

Describing the Mateens as "an all-American family", Zaidi elaborates: "His mom worked for a while at a daycare centre. They were pretty moderate as Muslims – none of the sisters or mom even wore a headscarf like some Muslims do."

But there's also an internet record of the Afghan-born father's more recent anti-US, pro-Taliban outpourings, in some of which he appears to believe that he is, or should be, the president of Afghanistan.

At the Islamic Centre of Fort Pierce, imam Syed Shafeeq Rahman​ tells reporters that Mateen had attended regularly since he was a child, coming to pray three to four times a week.

On finishing at the spectrum alternative school in 2004, Mateen attended Martin County's adult vocational school, where he reportedly struggled to pass his exams. Later, however, he was accepted at Indian River State College in nearby Fort Pierce, the Florida city that would become his home as an adult.

Chasing girls, going to parties, drinking

But as some recall, Mateen was ready to play, describing a life of chasing girls, going to parties and drinking. Ryan Jones, 27, who often went out with Mateen, tells the Post: "He was fun."

Samuel King, a school buddy, says that he and his friends hung out with Mateen at a local mall, where Mateen worked at a GNC store and King at a Ruby Tuesday restaurant. "Half the workers at the restaurant were openly gay," King says – including himself. "[Mateen] had to know it, but I never got any sense of homophobia or aggression from him – he always smiled, said hello, and treated us all like the individuals we were."

In 2006, Mateen graduated with an associate's degree in criminal justice technology and hopes – some real, some imagined – of a security services career.

And there was something else – as recounted by college friends, he was reaching out to gay men. Classmates concluded that Mateen was gay but was not open about it. One of them tells The Palm Beach Post that because his gang felt sorry for the socially awkward Mateen, they had taken him to at least four gay clubs in the Treasure Coast and West Palm Beach region. "He just wanted to fit in, [but] no one liked him," he says.

Subsequently, Mateen had asked him out "romantically", but the classmate had declined: "I was not out at the time, so I declined his offer."

On leaving college, Mateen worked for six months as a correctional officer in a juvenile detention facility. He was into bodybuilding and seemingly harboured a wish to be a member of the security services – he posed for selfies in an NYPD T-shirt; and a bumper sticker on a silver Toyota Camry still parked outside the Woodland Condominium in Fort Pierce, where he lived in Unit 107, claims that he is a US Marine.

Omar Mateen taking a selfie in an NYPD T-shirt. 

Finally, in 2007, Mateen landed a job with global security firm G4S Security Solutions, which says in a sparsely worded statement that Mateen was appointed to the G4S security staff at a residential community in Port St Lucie, and that there had been no adverse findings when he was subjected to company screening on being recruited in 2007 and again in 2013. Parallel screening by "a US law enforcement agency" had produced no findings on Mateen, who also did shifts at a local golf club and at the St Lucie County Courthouse complex.

Two ugly traits

Mateen soon revealed two ugly traits – according to his first wife, Sitora Yusufiy, he subjected her to physical abuse; and according to his security company colleagues, he would lash out angrily at blacks, women, lesbians and Jews.

He met Yusufiy online in 2009 – apparently she found his messages on the MySpace dating site to be alluring and funny. She also saw Mateen as the "perfect" resolution to a conflict with her family – he was sufficiently American for her free spirit and Muslim enough to please her traditional parents. "He was from my culture and, you know, had the same religion," she says. "So I was like, OK, this could potentially satisfy my parents." They married within months and moved to a two-bedroom apartment in Fort Pierce.

Originally from the central Asian republic of Uzbekistan, Yusufiy tells reporters that Mateen seemed "normal" – but the marriage lasted just nine months and in 2011 a judge deemed it "irretrievably broken".

She explains: "In the beginning, he was a normal being that cared about family, loved to joke, loved to have fun, but then a few months after we were married I saw his instability. He would get mad out of nowhere. That's when I started worrying about my safety."

Sitora Yusufiy, the ex-wife of Orlando shooting suspect Omar Mateen, and her fiance Marcio Dias. Photo: Autumn Parry

Outlining a catalogue of abuse, she says: "He started abusing me physically, very often, and not allowing me to speak to my family, keeping me hostage from them. [My family] had to pull me out of his arms and find an emergency flight ... I made a police report."

Recalling an evening when she had fallen asleep on the floor while waiting for him to come home, she says: "All I remember is being woken up by a pillow being taken from under my head … he started pulling my hair … he almost killed me … he started choking me. Somehow I got out of it and I tried to tackle him."

Yusufiy says Mateen was bipolar and she believes his mental instability was what made him angry and agitated.

He was also religious, she says, but she doubts religion had motivated Sunday's attack on the Pulse nightspot.

Yusufiy observed what she later would describe as "gay tendencies" in her husband: "After [our wedding] he confessed to me about his [recent] past, and [how] he very much enjoyed going to clubs and the nightlife … I feel like it's a side of him or a part of him that he lived, but he probably didn't want everybody to know about."

When Yusufiy is asked directly if Mateen was gay, she's ambivalent: "I don't know." And in a subsequent text exchange, in which an Orlando TV reporter asks if she knew Mateen used gay dating websites, she replies: "It seems likely."

At the same time, she reveals that Mateen's father suspected as much, describing a series of family rows during which Mateen's father accused him of being gay, which would be the cause of great shame and embarrassment in a religious Afghan family.

When they separated, Mateen moved to the Fort Pierce apartment in which he lived until his death early on Sunday – and in 2012 he struck up a relationship with a woman named Noor Zahi Salman, whose Palestinian parents reportedly came to the US and settled in the greater San Francisco area in the 1970s.

At the time of their meeting, the previously married Salman, now aged 30, was living in Chicago and though she and Mateen are widely assumed to have married, exhaustive media trawling of public records has produced only details of a jointly held mortgage in 2013, the year in which they also had a son.

Noor Zahi Salman, left, pictured with her husband, Orlando gunman Omar Mateen, and their son. Photo: Facebook

At about the same time, Mateen was first noticed as a presence at Pulse, a gay and Latino hangout that had thrived as a popular LGBT hangout in Orlando for more than 20 years – a refuge, a place to feel safe and, as needed, to raise funds. At times he was drunk; at others obstreperous.

Chris Callen, who has performed as a drag queen at Pulse, tells reporters: "I've seen him a couple of times at Pulse. A couple of other people that I've spoken with, including an-ex security guard, have actually witnessed this guy at Pulse many times before."

Callen's partner, Ty Smith, is more explicit, claiming to have seen Mateen at the club "at least a dozen times". Smith recalls: "[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. We didn't really talk to him a lot, but I remember him saying things about his dad at times. He told us he had a wife and child."

Jim Van Horn is a Pulse regular who recalls that friends called him away from the bar where he had spent an evening chatting with Mateen, because they worried that Mateen was "strange". Van Horn tells Associated Press: "He was trying to pick up people. Men. He was a homosexual and he was trying to pick up men. He'd walk up to them and then he would maybe put his arm round them or something ... That's what people do at gay bars. That's what we do."

A regular user of gay hook-up apps

Mateen also appeared to be a regular user of gay hook-up apps like Jack'd and Grindr. Former Navy serviceman Kevin West, 37, said Mateen messaged him via Jack'd over a period of years, most recently a few months before the Sunday attack, when Mateen told him that he was in Orlando and wanted to catch up for a drink.

Mateen had also messaged 23-year-old Cord Cedeno, who told The Washington Post he had seen Mateen at the club. "It was definitely him. He'd come in for years, and people knew him," Cedeno said. "He was open with his picture on the sites … I recognised him off Grindr."

In the same period, through his second "marriage", Mateen's isolation and anger troubled many who made contact with him. At the Islamic Centre in Fort Pierce, the imam tells a reporter: "He will come the last minute; he will leave the first minute. He will finish his prayer, and he will just leave … We would not see friends around him."

A neighbour describes him as rude and sullen, and unresponsive to simple pleasantries. "You'd say good morning, and he'd just stare back, or walk past without saying anything," says Jason Beers, 41, who lived a few doors down. "After a few times, you just stop saying hello."

In the Port St Lucie residential community where he manned a gatehouse, Mateen made people feel uncomfortable. Recalling a pattern that began last year and continued until this month, resident Jasmine Kalenuik​ says: "He asked me for my ID, and when he gives it back he just holds onto it … and he's clinging to it, and breathing weird and smiling at me with this crazed stare."

Kalenuik's husband, Jerome, also found Mateen unnerving: "There was something different about him. He didn't even give a flicker. He had a blank face, a poker face. He had that look ... It was almost like there was a shell around him."

Former G4S colleague and ex-local cop Daniel Gilroy, 44, complained that Mateen was "unhinged and unstable" – and he complains further that the company refused to act on his complaints. "I complained multiple times that he was dangerous, that he didn't like blacks, women, lesbians and Jews," Gilroy tells a local newspaper. Once when an African-American man had driven past, Mateen used the N-word in expressing a wish that he could kill all black people, Gilroy says. "He was always angry, swearing, just angry at the world."

Gilroy said he quit in 2015 when Mateen began harassing him, sending as many as 20 to 30 text messages a day and leaving him as many as a dozen phone messages. But in two instances, first in 2013 and again in 2014, the FBI investigated Mateen – and found nothing.

Spurred to action by G4S co-workers who heard Mateen claim he had links to foreign terrorists and that he hoped the FBI would raid his family home so that he might die as a martyr, the FBI put Mateen on its terrorist watch list for almost a year.

Investigators from the office of the medical examiner at Pulse nightclub where a gunman opened fire on Sunday. Photo: AP

At a Washington press conference on Monday, FBI director James Comey​ reveals that an undercover informant had made contact with Mateen, wiretapping their conversations and investigating his personal and financial records. Brought in twice for FBI interviews, Mateen claimed to have spoken "in anger" because his colleagues had ridiculed his Muslim background.

But what Mateen was accused of saying didn't make sense – he claimed a family connection with al-Qaeda; and at the same time, that he was a member of Hezbollah. One is Sunni and the other is Shiite – and they are bitter enemies in the Syrian war.

Intelligence officials in Saudi Arabia were enlisted to investigate Mateen's pilgrimages to the holy city of Mecca, for a total of 18 days in 2011 and 2012, but when nothing "derogatory" was found, Mateen's name was deleted from the watch list.

Mateen's name came back on to the FBI radar in July 2014, when an investigation into the activities of a Florida man who had travelled to Syria and carried out a suicide bombing revealed that he had attended the Fort Pierce mosque and known Mateen "casually", Comey says.

The man was Moner Mohammad Abu Salha – who was four years behind Mateen at Indian River State College and whose home was close to Mateen's. Again, Comey says, no reason was found to pursue the investigation.

There may have been another rupture in Mateen's personal relationships at the end of 2015 – there are reports that in December his second wife had moved out and was staying with relatives in California. But it seems she returned.

Clues in planning Pulse nightclub assault

There is no clear timeline on when Mateen began what investigators described as him "consum[ing] a hell of a lot of jihadist propaganda", as revealed by analysis of his electronic devices; just as there's no timeline on any detailed planning for the Pulse assault.

The first real clue, in a CNN report, is that in April and again early in June Mateen was observed making visits to both Pulse and to Disney Springs, an Orlando retail and entertainment complex run by entertainment conglomerate Walt Disney World. His movements were captured by surveillance cameras and reveal that he was accompanied by his wife Salman.

Also, analysis of phone tower data pinpoints Mateen's presence at the retail complex for a period of several hours on the day before he stormed the Pulse nightclub. The dates of Mateen's recorded movements overlap with Orlando's calendar of gay pride events, prompting investigators to examine a possibility that the gunman might also have considered the Disney complex as a target.

Around the same time, Mateen took delivery of his newly ordered weapons after a prescribed waiting period – a .223 assault rifle made by Sig Sauer and a Glock 9mm handgun, which he purchased from a gun range and stored about 25 kilometres from his Fort Pierce home.

Salman is co-operating with investigators to whom, according to NBC News, she has revealed she might have had knowledge of her husband's plot – she had accompanied him to buy ammunition and a holster; she had once driven him to Pulse; and she had failed in an attempt to talk him out of it.

The former Navy serviceman Kevin West, who Mateen had reached out to via Jack'd, never actually met Mateen until the early hours of last Sunday morning.

At about 1am, West was dropping a friend to join about 300 partygoers at Pulse when he recognised Mateen crossing the street – he was wearing a dark cap. "He walked directly past me. I said, 'Hey', and he turned and said 'Hey' and nodded his head," West told the Los Angeles Times. "I could tell by the eyes."

Orlando police chief John Mina says that most of the victims were shot in the first stages of the three-hour massacre drama and that when Mateen engaged officers in a series of phone conversations, he was utterly "cool and calm" as he made various claims of allegiance – to IS, to the Boston Marathon bombers – and misled them into a belief that he had planted explosives.

A survivor, who would be quoted only as "Orlando", told The New York Times that he was struck by the calmness in Mateen's voice as he warned some of his hostages not to text anyone: "He said, 'Please don't text'. That was the words he used."

Mateen took their phones and maintained that calmness when he called 911, pledging himself to IS, calling for the US to cease bombing Syria and threatening a greater loss of life if the police stormed the building.

Orlando says that at one point Mateen asked some of the hostages: "Are you guys black? And then he said: 'I don't have an issue with the blacks." He made no mention of gays.

He laughed as people begged him not to shoot

Orlando described how he feigned death through bizarre periods of quiet, in which Mateen fiddled with his weapons and used the sink and a hand drier. At times Mateen checked the bodies around him, including that of Orlando, who said that he felt himself being poked.

Another survivor, Norman Casiano, hid with others in a bathroom stall, saying he could hear Mateen laugh as people begged him not to shoot, with some offering assurances that they would never be able to identify him. "All I heard was a laugh," Casiano said. "He laughed like an evil laugh, something that's just going to be imprinted in my head forever." It was, he said, "a laugh of like, 'Ha, I did it'."

Mateen's father, Seddique, dismissed his son's pledge of loyalty to IS as nonsense: "I think he just wanted to boast of himself. No radicalism, no. He doesn't have a beard even ... I don't think religion or Islam had anything to do with this."

Seddique Mateen is the father of Orlando shooter Omar Mateen. Photo: YouTube

And on Monday, the father was playing down his own suggestion of the previous day – that Mateen had been upset because recently he had witnessed a gay couple kissing and touching in Miami. Now he tells an interviewer that the importance of the incident had been overblown: "That was a couple of months ago and he never talked about it afterwards. I don't think that incident would trigger this kind of violent reaction."

If an inability to cope with his own sexuality ignited Mateen's murderous rampage, the irony is that IS would behead him if he ever revealed himself as gay.

Questions of Mateen's motivation are being greatly magnified in the contest for control of America's presidential election campaign.

This country has a long history of senseless massacres, sparked by real or imagined slights or internal conflicts on the part of the perpetrators, that have nothing to do with a more contemporary intrusion of radical Islamist ideology.

And we've never heard tell of a gay jihadist, even though Mateen was embraced by IS within hours of the attack and condemned as an IS footsoldier by Republican presidential contender Donald Trump.

But in a sense Mateen's sexuality no longer matters, because his propaganda and political shelf life has expired – IS can kick back and watch the US in convulsions after Orlando; and Donald Trump is having the debate he wants on the terms that he wants. To that end, it matters hugely that Americans understand what motivated a man who has so chillingly revealed himself as anything but what his seemingly eccentric father called him – "a good boy".