The relationship between Heather Mack and her mother had grown increasingly strained

By Johnny Dodd
September 28, 2016 11:25 AM

In an exclusive audio interview from a prison in Bali, Heather Mack reveals the tragic events leading up to the headline-grabbing murder of her mother and the real reason her body was stuffed into a suitcase.

“I think it was half premeditated and half not,” Mack, now 20, tells the TV newsmagazine Crime Watch Daily, describing how her boyfriend killed her mother, Chicago socialite Sheila von Wiese-Mack, 62, during a vicious early morning argument in her upscale Saint Regis Bali resort hotel suite. (The audio interview was temporarily shared exclusively with PEOPLE.)

“In my head I never thought it [the murder] was going to happen, but in my heart sometimes I wanted it to.”

Mack’s boyfriend, Tommy Schaefer, 22, confessed to the killing during the couple’s trial in 2015, in which they both faced death by firing squad. Schaefer ultimately received an 18-year sentence and Mack was sentenced to ten years in Bali’s infamous Kerobokon prison.

In Mack’s most recent interview, scheduled to air on the one-hour program on Sept. 29, she discusses the toxic, troubled relationship she had with her mother – which was examined in a lengthy account in PEOPLE last year.

Their relationship grew increasingly strained after the 2006 death of her father, the renowned Chicago-based jazz and classical composer James Mack. By the time the time Mack and her mother left for their fateful August 2014 vacation in Bali, many who knew the pair were fearful of what might happen.

“One night it was horrible,” Mack says, explaining why she decided to have Schaefer fly to Bali to join her. “She was so drunk and I said, ‘Tommy, I need you to come here. I can’t take this anymore. I’m going to kill myself.'”

Heather Mack (left) and Tommy Schaefer
Firdia Lisnawati/AP

Schaefer, whose $12,000 plane ticket was paid for with Sheila’s credit card, arrived at their hotel shortly after midnight on Aug. 12. Mack’s mother “went nuts,” says Heather, when she learned that the aspiring rapper had flown to Bali and booked a room using her credit card. Shortly after he arrived, she confronted him in the hotel lobby.

After the blowout, Sheila and her daughter returned to their room, but Mack eventually snuck out and met up with Schaefer, once again telling him, “‘I can’t take it anymore. I can’t do this,'” she says. “And Tommy said, ‘Let me talk to her.’. . . And that’s when it began.”

Minutes later, Schaefer arrived at Sheila’s room. Mack claims she informed her mother that she was pregnant with Schaefer’s child, which, she says, prompted Sheila to “run around the room, looking for a knife, screaming that I was going to die.”

At one point, Sheila allegedly grew so enraged that she “grabbed” Schaefer around the neck. “Tommy could have shoved her off,” she says. “He’s a strong man. But I was screaming and screaming and he just smacked her over and over and over.”

Mack insists that she fled into the bathroom during much of the beating, which police investigators said involved a metal fruit bowl.

As her mother lay on the floor, slowly asphyxiating as a result of the extensive injuries to face, Mack recalls Schaefer trying “to hug me and he had blood all over his shirt. I remember thinking, ‘Why is he hugging me with my mother’s blood all over his shirt?’ . . . At that moment I turned to ice and I didn’t melt for six months.”

Hours after the murder, the couple placed the suitcase in the trunk of a taxi before fleeing the hotel. The driver notified police after he spotted blood leaking from the luggage.

Heather Mack
Agung Parameswara/Getty Images

Mack, who is currently raising the 18-month-old daughter she had with Schaefer in prison, insists that the decision to stuff Sheila’s body into a suitcase was her idea.

“Tommy said, ‘We have to run.’ And I said, ‘Are you nuts?’,” she says. “I was just hugging her and hugging her. I wouldn’t let her go.”

“What do you want to do?” Mack claims Schaefer asked her.

Her reply is as chilling as it is poignant. “I said, ‘I want to bring her [with us],'” Mack recalls. “‘I want to bring her in a suitcase. I’m not leaving her here.'”

For more, tune into Crime Watch Daily with Chris Hansen on Thursday, September 29.