For nearly three years, Kallista Mutten has carried the unbearable weight of losing her daughter, Charlise, at the hands of someone she trusted.

Now, for the first time, she is sharing her story, not just to speak her truth, but to tell the world she is not the villain many have painted her to be.

Watch: Sneak Peek Catching A Child Killer 60 Minutes Australia. Article continues after video.

When Kallista first met Justin Stein in 2018, she was in a dark place.

The pair crossed paths in prison—a seemingly chance meeting during renovations when male and female inmates shared the same visiting area.

At that time, she believed she had found someone who understood her pain, someone who, like her, wanted to turn his life around.

But as Kallista heartbreakingly admits now, it was a mistake that has haunted her ever since.

Her daughter Charlise Mutten, just nine years old, was brutally murdered by Stein in January 2022.

She had been living in Queensland with her grandparents, and was only visiting her mum and Stein in the Blue Mountains for a few weeks over the school holidays.

Police were told the little girl was last seen on Thursday, January 13. Her mother reported her missing on Friday morning.

Five days of searching later, police found a barrel on the banks of the Colo River. Charlise's body was inside. She had been shot once in the head and once in the lower back. Police also found 99kg of sand that had been used to try and weigh down the barrel.

Stein was charged with murder the day they found her, and was found guilty in 2024, given the maximum sentence of life imprisonment.

"I regret putting relationships first. I hate myself for it. I really do. It's taken this for me to wake up and realise that I already had someone that loved me unconditionally, and he took that away from me," she told 60 Minutes Australia, breaking her silence for the first time.

Kallista trusted Stein with her daughter, hoping he could fill the fatherly role Charlise had longed for. But instead, Stein became the monster who shattered her family.

While the world has placed much of the blame on Kallista, she is adamant that she has no idea what darkness is hiding behind Stein's facade.

"I didn't commit any murder or anything like that, but I do take accountability for the things I have done," she said.

Kallista Mutten has broken her silence. Image: 60 Minutes.

"I'm not this monster people think I am."

Kallista's life was spiralling out of control when Charlise came to Sydney for what was meant to be a joyful summer holiday. She had been struggling with ice addiction at the time, was trying to get her life back on track after years of hardship.

"I'm not this monster that everyone has read in the papers and the news," she asserted.

Charlise, who had been living with her grandparents since the age of four, was excited to spend time with her mum and Stein, who promised to be the father figure she had always wanted.

"He said in the car, 'I'm always gonna be a father figure for you, Charlise. You can call me Daddy.' She'd always longed for a dad, and in that moment, I believed him," Kallista said, reflecting on the conversation.

Justin Stein and Kallista Mutten. Image: Facebook.

But just weeks later, that promise of family was cruelly ripped apart when Stein took Charlise, and, in an unimaginable act of violence, shot the little girl in the face.

Kallista had no reason to suspect danger when Charlise asked, "Can I go with Daddy, Mum?" Her response, one that replays endlessly in her mind: "Of course you can."

"I didn't think anything of it, and that's the last time I saw her," Kallista recalled.

Charlise Mutten. Image: Nine

"Everything was lies."

What happened next is a web of lies and manipulation that Kallista admits she fell for.

Stein texted her, reassuring her that Charlise was fine, happy, and playing.

She had no idea that while she was waiting for them to return, Stein was alone at a Mount Wilson property, hours deep into dating sites and pornography, plotting the most horrifying crime imaginable.

When Charlise didn't return, Kallista's world truly began to unravel.

She says she tried to believe Stein's stories, that Charlise was safe with a family friend or that she had been kidnapped by criminals from his past.

"It was just all lies. Everything was lies," Kallista told 60 Minutes, explaining that her fear and addiction clouded her judgment at the time.

"But I held on to hope that she was okay."

But Stein's lies couldn't fool detectives, who were already suspicious from the moment Charlise was reported missing.

Image: Nine

In the days following, hundreds of police and emergency services searched for her.

Dogs, helicopters, SES volunteers and locals all spent five days combing the dense Blue Mountains bushland.

Through painstaking detective work and hours of CCTV footage, police traced Stein's movements and discovered Charlise's body stuffed into a barrel on the banks of the Colo River.

She had been shot once in the head and once in the lower back. Police also found 99kg of sand that had been used to try and weigh down the barrel.

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While searching for Charlise, police had also been retracing Stein's movements. They allege he bought sandbags, refuelled his boat, and visited the Colo River in the days before the little girl was reported missing.

They have CCTV footage of the 33-year-old at a BP towing a boat, in the back of which, is allegedly the barrel containing Charlise's body.

He was charged with murder the same day they found her.

Detective Sergeant Brad Gardiner, who led the investigation, said there was nothing Charlise could have done to justify Stein's actions.

"There is nothing a nine-year-old could do to an adult who is there to protect her that could justify any outcome for what happened."

"I forgive him, but not for what he's done."

Kallista's heartbreak didn't end with Charlise's death. In his final despicable act, Stein tried to claim that Kallista was responsible for her own daughter's murder.

"As I found out that he was saying I did it, that's when I knew that he'd done this," she said. "It was another horrible moment—I had let this person in, trusted him, and believed everything he told me."

It took a jury just three weeks to find Stein guilty of Charlise's murder.

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He was sentenced to life in prison without parole, joining the ranks of Australia's most heinous criminals. But for Kallista, no sentence will ever bring back her daughter or erase the guilt she feels.

"I forgive him, not for him but for me," she said tearfully. "So he has no power over me anymore."

Kallista's road to recovery is ongoing. She is now clean, but the pain and guilt of losing her daughter will never leave her.

Image: Nine

Still, she is determined to rebuild her life and honour Charlise's memory, carrying with her the one constant that can never be taken away—the love her daughter had for her.

"I do have her in my ears saying, 'Remember Mum, my opinion only matters, and you're the best mum in the world,'" Kallista said.

"No one can ever take that moment away from me."

If this has raised any issues for you, or if you just feel like you need to speak to someone, please call 1800 RESPECT (1800 737 732) – the national sexual assault, domestic and family violence counselling service.

Feature image: 60 Minutes.