The Monterey Park killer Huu Can Tran, 72, was an 'unhappy' man without 'family, money or a future' who had built up a store of grievances against his ex-wife, and the owners and instructors at the two dance halls where he massacred 11 people on Saturday night.
Speaking in an exclusive interview with DailyMail.com, a former friend who asked not to be named for fear of a backlash, described Tran as mistrustful of other people and paranoid.
He said: 'He was very distrustful of people and he was angry towards lots of people.
'He spent years accumulating unhappiness and disgruntlement towards people.
Huu Can Tran, 72, shot himself on Sunday in a van after being surrounded by SWAT teams. His motive for the rampage at Star Dance Studio remains unconfirmed, but police sources say it was a 'domestic dispute'. He is shown in surveillance footage from Saturday
Floral tributes pile up at the site of the weekend massacre carried out by Huu Can Tran
People left floral tributes at the site of one of the shootings on Monday throughout the day
'He was always complaining about people, especially the bosses of those two studios and the instructors who worked there. He would say, 'they're not nice to me' and 'they're saying evil things behind my back'.
'I think he was paranoid, delusional.'
The 76-year-old man said he first met Tran over a decade ago, when he rented an apartment in Arcadia, California from him.
He said things had initially gone well, and that he had always paid his rent on time.
But that changed when Tran sold the apartment and the two men moved into a different property together.
Hero Brandon Tsay, 26, wrestled the gun out of Huu Can Tran's hands after he showed up at the Lai Lai Ballroom and Studio in Alhambra on Saturday night looking for more victims. Tran, shown in a hat and wearing all black, had just killed ten people at another studio
Shortly after he was spotted at the hospital for treatment, Tran was pulled over by police. A SWAT team swarmed the van after a three-hour long standoff
He says they had begun the tenancy as friends but that changed after he took a month-long vacation in Taiwan.
The former friend said: 'When I came back, I found a cold shoulder and a stone face.
'He wouldn't talk to me at all.'
When the friend moved out, Tran then attempted to withhold his $750 security deposit - claiming he had broken a sink when it had merely been left dirty.
The dispute eventually ended up in court - the judgment, awarded in January 2015, went against Tran and he was ordered to repay the money plus $300 in costs.
'He was trying to find all sorts of reasons for the deposit to be gone,' the ex-friend said. 'I won the case and as soon as we stepped out of court, he cut me a check.
'That was the last time I saw him - I didn't want to see his face again.'
The former friend says Tran would also complain about his ex-wife Helen Lai, 59, who he divorced in 2006 citing 'irreconcilable differences'.
Monterey Park mayor Henry Lo kneels at a makeshift memorial outside the scene of a deadly mass shooting at a ballroom dance studio on Monday in Monterey Park, California
People mourn outside the entrance of the Star Ballroom Dance Studio after a mass shooting during Chinese Lunar New Year celebrations in Monterey Park, California
The Star Dance Studio in Monterey Park, which was targeted on Saturday night
Tran was also identified as the man gunman who entered the Lai Lai Ballroom in nearby Alhambra just 20 to 30 minutes after the first shooting, but brave patrons thwarted his attack
Court papers obtained by DailyMail.com show the pair were married between June 2001 and separated on December 31 2005, with the quickie divorce signed off by May 9 2006.
According the papers, it was alleged mass murderer Tran who filed for divorce and he represented himself during the proceedings.
In his divorce petition, Tran requested 'all assets, earning, properties acquired and debts incurred before marriage and after separation.
'All assets and properties acquired by gift, inheritance, or devise.'
A copy of the settlement shows Lai agreed to his request – the former couple split their assets based on who had what when they married and each allowed the other to keep money they personally earned during the marriage.
The former couple also agreed not to ask for spousal support from each other and waive any claim to each other's homes.
The struggle was at the Lai Lai Ballroom & Studio in Alhambra , the gunman's second stop
Despite the amicable-sounding arrangement, police in Hemet, California, have revealed Tran twice complained about 'past fraud and theft' by his family in recent weeks.
According to a statement released Monday, Tran visited the police department on January 7 and 9 where he alleged 'past theft, fraud, and poisoning allegations by his family in. the Los Angeles area 10 to 20 years ago' – a time period that corresponds with his marriage.
The statement continued: 'Tran stated he would return to the station with documentation regarding his allegations but never returned.'
Tran's friend said he never mentioned poisoning to him but had believed she 'tricked' him into selling his trucking business.
He said: 'Sometimes he would mention his wife and how she used to work at his trucking business. He said she tricked him into selling his truck and his business.'
Lai briefly spoke with CNN on Sunday evening and told the outlet Tran could be 'quick to anger' but was never violent towards her.
After an hours-long standoff, Tran died of a self-inflicted gunshot wound in the van he used to flee after his attempt at a second shooting that was thwarted by 'hero' patrons on Saturday
She told how the pair met at the Star Ballroom Dance Studio – the Monterey Park venue that was the scene of the Saturday evening mass shooting – where he had introduced himself and offered free lessons.
After they married, he would become upset if she missed a step dancing because 'he felt it made him look bad'.
The pair split after four years when 'he lost interest in her', according to Lai.
On Monday, Lai's home in Rosemead – just over two miles from the scene of the massacre – was deserted when DailyMail.com visited.
Neighbors told DailyMail.com that the 59-year-old has not been home since Sunday night and do not know where she went.
The friend, meanwhile, says he is not surprised by what happened and believes Tran chose Lunar New Year because in Chinese culture, the date represents the closure of an era.
He said: 'Chinese New Year is the end of a period and I think he chose this time to make it complete.
'He had accumulated so much hatred and I think he wanted to end it there. I knew this would happen one day - he hated so many of the people working at the ballrooms.
'He was getting older, he had no happiness, he had no family, no money and no future. People in those circumstances do crazy things.
'It's just so unfair - the people he killed were innocent.'
