WWhat drives a woman to murder her husband, run away and murder another woman at the same time?

That's the central question of a two-part HBO documentary I'm Not a Monster: The Lois Riess Murders Airing October 15th and 16th, with Lois Riess, a Minnesota woman serving two life sentences for the 2018 murders of her husband David Riess in Blooming Prairie, Minnesota, and Pam Hutchinson, a woman she met on the island Run in a bar in Fort Myers Beach.

Riess was arrested in April 2018 when George Higginbotham, then manager of the Dirty Al restaurant on South Padre Island in Texas, reported her to the U.S. Marshals after recognizing her CBS This Morning. She pleaded guilty to both murders.

For the documentary, director Erin Lee Carr interviewed Riess from prison to find out what was going through her mind as she committed these horrific acts.

Explore what drove Lois Riess to murder

Viewers will not find clear answers as to why Riess killed Hutchinson or her husband. But in the documentary, Riess talks about her turbulent marriage and sheds light on her mental state in the time before the murders. She says her husband, who ran a lucrative business extracting wax worms for fishermen, physically and verbally abused her and their children.

“He threw things away and smashed things that were important to me, like pictures,” Riess says. Then she says he got to the point where “all I had to do was push and hit.” She describes not feeling like she had a way out and that she experienced “a lot of verbal abuse, which I think is worse than physical abuse.”

Kari Schirber, a friend of Lois Riess, backs up her claim in the series by saying, “He was a hothead.”

What was really going on in her marriage was a mystery to many of her family members. Carr tells TIME: “She never said anything about marriage, and so (her husband's murder) was a shock to everyone who knew her, everyone who covered the story.” Carr adds: “It's coming “It seems to people like she just had a gambling addiction and insulted him because he cut her off or something.”

But based on many interviews with background sources, Carr says, “Lois was in a toxic, abusive relationship.” At some point during their marriage, Riess was admitted to a psychiatric treatment facility after attempting suicide, and her husband visited her only once. Carr says something may have broken inside her at that time.

Lois Riess and a history of mental health issues

The documentary explores how a gambling addiction may have contributed to her making impulsive decisions and even features a gambling addiction specialist talking about what's going on in a gamer's head. Riess obtained her entire inheritance through gambling. While on the run, she frequented casinos after exploiting her husband's personal and business accounts. “The only thing that made me feel good was playing,” says Riess. “Gambling is the worst drug of all. It's like a kind of euphoric high. You feel special.”

Throughout the documentary, Riess expresses regret for both murders and blames mental illness for her actions, but does not discuss a specific diagnosis. Several members of her immediate family suffered from mental health problems and her mother died in a mental institution.

When police officers found Hutchinson dead in her apartment on April 9, 2018 – identification and credit cards missing – they considered Riess the prime suspect and believed she killed Hutchinson because the two looked similar. When asked how she ended up chatting with Hutchinson at the bar and then killing her, Riess replies: “When I say it's a mystery, it really is a mystery because I don't have all the memories and all the answers to it.” She adds, “Mental illness – the mind is a crazy thing.” All I know is that it happened.” Hutchinson, she says, “just got caught up in my breakdown.”

It's rare for a murderer to appear on camera, but Carr told Riess that addiction and mental health issues run in her own family, too. She is the daughter of the former New Yorker Just Columnist David Carr, whose memoirs The Night of the Gun is a harrowing account of his struggles with drug addiction. And she herself has been sober for 9 years. She argued that she could approach the interview with a measure of understanding – although she still can't fully understand what drove Riess to commit two murders.

“I found that she was unable to take full responsibility for what she did,” Carr says.