When Dr. Thomas Burchard, a highly regarded child psychiatrist, connected online with Instagram model Kelsey Turner, the relationship quickly developed into an addiction. He was obsessed with the beautiful 25-year-old known as "Badd Barbie"; she was dependent on the money the doctor supplied for a lavish lifestyle.
But when Burchard, 71, decided he would no longer serve as Turner's so-called sugar daddy, the relationship ended with the beloved doctor's battered body found in the trunk of Turner's car in the Las Vegas desert.
Turner, her boyfriend Jon Logan Kennison, and their housemate Diana Peña were the last people to see Burchard alive.
The moment Kennison emerged from the garage of the home they shared covered in blood was one Peña will never forget, and she revealed the details in an exclusive interview with "20/20" airing February 24 at 9 p.m. ET.
"I'd never been so scared in my life. It's just like real terror. And then, I just kind of went numb," Peña told ABC News. "I just turned around and started washing dishes, because that was the only thing I could do to calm down."
Peña later became a key witness for the authorities, helping to piece together the final moments of Burchard's life.
When asked why she was telling her story now, Peña explained, "I just wanted to tell the truth. I get to say my piece and have a little bit of closure."
In early 2019, Kelsey Turner was in Las Vegas, living in a home and driving a car that Burchard was paying for. After months of bankrolling Turner's lavish lifestyle, Burchard decided to make a surprise visit to the home on March 1.
Judy Earp, Burchard's longtime girlfriend, recalled speaking with him on the phone later that day.
"His exact words were, 'Kelsey Turner is such a consummate liar. I just had to check things out for myself,'" Earp told ABC News.
The next day, when Peña finished her bartending shift, she asked Turner for a ride home. Burchard was driving the car when they picked up Peña. After Burchard got lost, he passed his phone to Turner so she could use his GPS.
Peña explained that Kelsey, "started going through his phone. And she saw some stuff that she didn't like...messages between her mom and Dr. Burchard...talking about maybe taking away her children."
All hell broke loose on the highway when the two started fighting with each other. And back at the house, the fight escalated, according to Peña. Turner's rage included threats to contact Burchard's employer with baseless claims of child pornography on his phone.
"[Burchard] seemed a little confused. He just kept saying he loved Kelsey and he didn't know why she was acting like that," Peña said.
Peña's first thoughts were for Turner's little boy. She had a trusted friend whisk him out of the house as the violence escalated.
Kennison ran upstairs, broke down the door to the room where Burchard had retreated and started hitting him with a baseball bat, Peña said.
"I just started screaming at them to stop and calm down," Peña said.
Peña said she told Turner and Kennison that they should take the injured Burchard to the hospital. They got him to the car, and Burchard said he wanted his jacket.
"He said, 'you know, they're going to kill me,'" Peña said.
Turner and Kennison went into the house, but when they returned, they instructed Peña to go upstairs and clean up the mess created during the bedroom fight while Burchard remained in the garage.
According to prosecutors, Kennison beat Burchard to death with a firearm as Turner encouraged him.
When asked why she thought Turner was willing to kill the man who had given her hundreds of thousands of dollars over the course of their relationship, Peña explained that it was because, "He didn't want to be her golden goose anymore. He was going to take it all away."
In emails, Turner once described herself to Burchard as a single mom with financial hardships who just needed a little help getting back on her feet, Earp told ABC News.
"He believed that everyone could be good, that no one was intrinsically bad. And, unfortunately, that's not true," Earp said.
Over the course of their relationship, Burchard gave Turner more than $500,000, for things like prescription drugs, money, rent for houses and access to cars, according to prosecutors.
Others close to Burchard said he became obsessed with Turner, telling them that the relationship made him understand how heroin addicts must feel.
"She was more like, 'Where are you at? I need money,' you know, 'I need these prescriptions right now. You better get over here.' And she would always say, 'You want some of that love, you better get over here,'" Burchard's friend, Eddie Mendoza, told ABC News.
Earp became fed up with the arrangement and told Burchard he had to cut off Turner. So Burchard kicked Turner out of the Salinas, California, house he was paying for and took away her BMW. At Earp's suggestion, Burchard gave Turner money to move to Las Vegas permanently.
But Burchard's obsession would soon resurface.
"I saw several texts where she needed more money, more money for everything," Earp said.
Burchard gave Turner a new Mercedes to replace the BMW and started paying Turner's rent on a four-bedroom house for Turner and her son. Turner kept Burchard in the dark on just about everything, including who was living in the house.
Along with Peña, another roommate slept in the bedroom next to the garage. Turner shared the master bedroom with Kennison, a former gang member whom she met in early 2019.
Earp filed a missing person report after Burchard didn't show up for his flight back home to California. Four days after the murder, his body was found in the trunk of Turner's car, which was abandoned on a desert road outside of Las Vegas.
Peña claims she went along with the couple as they fled to California because she feared for her life. She eventually convinced them to let her go back to Las Vegas, where Peña turned herself in to the police. Peña's charge was reduced from murder and she pleaded guilty to accessory to murder, in part because she provided important details to authorities.
In July 2022, Kennison pleaded guilty to second-degree murder and conspiracy. He was sentenced to 18 to 45 years in prison.
"I want to help others that were involved in similar situations to hopefully prevent the same from happening, and show people that toxic love situations aren't always what they seem," Kennison wrote in a letter to ABC News.
While awaiting trial, Turner gave birth. She took an Alford Plea, which allowed her to plead guilty to second-degree murder while still maintaining her innocence. She was sentenced to 10 to 25 years in prison.
Earp delivered a victim's impact statement.
"My entire world was viciously ripped from me with the murder of Thomas K. Burchard. I frequently dream that Tom has come home and it was all a big mistake. Then I realize that the real nightmare is waking up and knowing that he will never come home," Earp said.