The one-time boyfriend of a woman allegedly murdered by her identical twin has given a chilling new insight into the siblings' "toxic", chaotic relationship.
American exercise gurus Alexandria and Anastasia Duval (aka Alison and Ann Dadow), achieved international notoriety earlier this year after Alexandria was charged with murdering Anastasia by intentionally driving their SUV off a cliff in Hawaii.
Charges were initially dropped against the 38-year-old, who then fled to upstate New York, but were reinstated two weeks ago following the emergence of unspecified new evidence.
Why would twins try to kill each other
Eyewitnesses who had been driving behind the sisters told investigators the pair appeared to be engaged in a physical fight and that Anastasia (who was in the front passenger seat) could be seen pulling her sister's hair in the seconds before the fatal plunge.
For Keith Weiss, hearing those details was like déjà vu; he had experienced first hand what it was like to ride in a car while the warring twins were in full flight and it had been terrifying.
The Florida chef dated Anastasia (then known as Ann) for six months more than 10 years ago, long before their Twin Power yoga school turned them into minor celebrities.
Weiss says there were at least two occasions when "very intense" fighting between the sisters inside his car almost resulted in a crash.
"The first time, Ann was driving, and they just started fighting," he said.
"She let go of the wheel and they were going back and forth with each other, oblivious to the obvious danger and the other cars around us. She almost lost control of the car."
The second incident was so bad that Weiss called it quits with Ann shortly after.
"We were driving home and they wanted me to stop so they could get some wine," he recalled. "But I didn't want to stop, and Ann, she started kicking my hands ... kicking them off of the steering wheel. Alison (now known as Alexandria) was kicking the windows and they were screaming, 'I want you to stop!' I told them, 'You're going to end up killing us'.
"They didn't care."
'GET OVER HERE NOW ... I'M GOING TO KILL HER'
While the incidents read like a prelude to the fatal crash in Hawaii on May 29, they are just two of many disturbing clashes Weiss witnessed during his six-month romance with Ann.
The twins had been in their mid-20s and enrolled in a stenography course when he first crossed paths with him. Alison would frequent the South Florida restaurant where he worked at the time and the pair struck up a friendship.
One day she came in with her twin sister. The young chef hit it off with Ann and the pair began dating. Alison, however, would almost always accompany them.
"It almost seemed like Alison was jealous of Ann, who always got the guy," Weiss told People.
"Alison was just a bystander, basically. Alison was always the one who was tagging along."
Weiss described the twins as having a "toxic" relationship that never seemed to let up.
"There was just so much drama," he said. "They would really get into it. I remember this one time, the three of us were at the mall, and Ann smacked Alison in the back of the head. Hard.
"They raged. They went back and forth with each other, pulling hair, pinching each other ... it was as if they had blocked everything out around them."
The acrimony between the sisters intensified the more alcohol they consumed. When they drank, bad things would happen.
"I once got call from Ann saying, 'Get over here now ... I'm going to kill her'," he said.
"She actually started hitting Alison with the phone. I heard it ... thump, thump, thump. They were both screaming at each other.
"I get to their apartment and there's broken glass everywhere from wine bottles and shattered glasses. There was blood everywhere, and the bedroom door was falling off its hinges. Both of them were sitting on the couch when I walked in, and they were like, 'Hey ... how are you doing?'
"Alison had a bruise on her face. I asked them if they were OK, and they were like, 'We're good, we're fine. We're just watching a movie'. Meanwhile, all around them it's total destruction. They seemed to not know they wanted to kill each other just minutes earlier."
'THEY SEEMED TO HAVE A LOT OF DARK DEMONS'
The fatal crash followed years of failed business ventures, personal bankruptcies and moves for the sisters, who first made a name for themselves as yoga instructors in Florida.
As Alison and Ann Dadow, they founded Twin Power yoga, setting up their first studio in Palm Beach Gardens in 2008 and opening a second in West Palm Beach in 2011.
"They were alpha females on top of being twins on top of being very dominating," personal trainer Victor Ayala, who worked at a gym on the same floor as the twins, told The Palm Beach Post.
"They were fantastic teachers, beautiful women, but I also know they were very competitive and very strong-willed. They seemed to have a lot of dark demons."
While they had no shortage of students, with many crediting the twins with improving their lives by introducing them to yoga.
Others claim they were desperate to be famous and abused the trust of clients and employees alike in their quest for fame and fortune.
"They were wolves in sheep clothing. They used yoga as a mask. They wanted nothing more than to be rich and famous," the former employee told The Post. "They were very authoritative and not empowering."
Their show business aspirations almost paid off when the Dadows entered talks with a TV network about launching their own reality series.
But their "constant bickering" and "struggles with alcohol" led to increasingly erratic behaviour.
They started shooting bizarre promotional videos together while riding in a Porsche and writing unflattering segments about staff members behind their backs.
A former Twin Power yoga teacher recalled the twins berating her for making changes to a class instruction plan without their permission. "I walked away and they followed me into the bathroom (demanding): 'Are you going to cry?'
"I started taking anxiety medicine to teach classes for them because they were giving me such anxiety. I shouldn't need anxiety medicine to teach yoga class. That doesn't make any sense."
At the network's urging, the Dadows spent a small fortune on renovations, only for the show to be canned at the last minute.
West Palm Beach psychic Leslie McMichael, who claimed to have acted as the twins' spiritual adviser, told The Associated Press the show's axing contributed significantly to their spiral into debt.
In 2014, they abruptly packed up and left town for Utah, allegedly without paying several staff members.
Bizarrely, they kept their business name, opening a Twin Power yoga studio in the picturesque mountain resort town of Park City but changing their names to the more theatrical sounding Alexandria and Anastasia Duval.
'MOST BIZARRE YOGA EXPERIENCE I'VE EVER HAD'
Park City locals were intrigued by the striking, identical blondes and business was initially good but once the novelty wore off, the cracks in their relationship began to show.
Former students at the Park City studio say classes with their pair were excruciating, with the sisters issuing rapid and conflicting instructions.
"It was very frenetic and disorganised," one woman who attended a session told People magazine on condition of anonymity.
"They were teaching at the same time, speaking over one another really fast: 'Do this, lift your arm, lower your left arm'. It was honestly one of the most bizarre yoga experiences I had ever had.
"They were giving instructions that didn't seem to be making much sense to me and at the same time, they were both assisting me. It was a very unusual experience in the yoga community ... I'm sure any regular practitioner or teacher would agree."
The woman said she attended one of their evening classes but nearly walked out when "they made fun of my pose".
"(It was) rude. You never want to demean someone's personal experience, but also, yoga is about your personal experience."
She also claimed the sisters would "pseudo-spiritual speak that didn't mean anything" and noticed that "a lot of their information was incorrect - it was just incorrect."
"It wasn't necessarily about me," the woman said of the vibe she got from the class. "(The sisters) had "a weird dynamic ... I wasn't sure if they were trying to impress me or each other".
After the fatal crash and Anastasia's arrest, the woman started asking around about the Duvals.
"I did hear other students say that they had some similar experiences to me, where they were just bizarre and chaotic and disorganised," she said.
"(Both twins) were equally chaotic and based on my interaction with them, just distracted, ungrounded, unorganised."
Alexandria Duval has been languishing in a New York jail cell since she was rearrested on November 11 for the murder of her sister.
The 38-year-old, who suffered serious injuries in the crash that killed her sister, is resisting efforts to extradite her to Hawaii.
Prosecutors allege Duval intentionally caused the death of Anastasia when she allegedly drove their SUV off the ocean-side Hana Highway in Maui.
Witnesses claim they saw the twins violently arguing moments before the driver seemed to suddenly accelerate and make a sharp left turn. The vehicle then slammed into a rock wall and plunged 200 feet to the rocks below, according to KITV in Honolulu.
After being discharged from the hospital, Alexandria was arrested and jailed in Maui on a second-degree murder charge. She had planned to plead not guilty, but a judge later ordered her release after determining there was no probable cause for a murder charge.
That changed last month when a grand jury in Hawaii indicted her for murder, citing unspecified new evidence.
Alexandria was scheduled to reappear in court on December 16.