They forgot their kids were in the car. The question everyone wants to ask is: HOW?

A life-changing mistake can be made in an instant.

For most parents, the idea of hurting their child is unthinkable. But for a tragic few, a small change to a daily routine is all it takes to turn the unthinkable into reality.

On tonight’s 60 Minutes, parents who left their children in hot cars to die tell of the unimaginable grief that follows such a fatal mistake.

For Kristie and Brett Cavaliero, their daughter Sophia (or Ray Ray, as they called her) was the most precious baby on earth.

“She was so beautiful. She was so perfect. She was such a good little girl,” gushes Brett. His wife Kristie agrees.

“I would say she was the perfect baby.”

But tragedy struck Sophia’s charmed life three years ago, when Brett strapped Sophia into her car seat and forgot to deliver her to daycare.

“He headed down the driveway and down the hill and, that morning, he turned right. And we don’t know what happened. We don’t know why,” Kristie told 60 Minutes host Michael Usher.

Throughout the morning, Brett had no idea that his little girl, who he had carefully dressed in a tropical-themed dress that morning, wasn’t at daycare where he believed he had taken her.

“In my mind, when I was at work, I just… I’m picturing her at day care with that tropical dress on and it’s never…never came to me that she was in my truck.”

It was only later that day, when Kristie picked him up for lunch, that the realisation hit home.

“We were driving down to a restaurant not far from his office and we were just talking about how cute she looked that day and he got really quiet. And I said, ‘What is going on?’ And that’s when he said, ‘I can’t remember dropping Ray off at day care.’ And my heart just sank,” Kristie told Usher.

The couple rushed back to Brett’s truck, but after four hours in the blistering heat, it was far too late for Sophia.

It’s a tragedy that neither Brett not Kristie has quite come to terms with.

“I still don’t know [how I could do that]. I still ask myself all the time but I’ll never get the answer to that.

“If it was a choice between taking one life or another, I begged, ‘Take mine,'” Brett admits.

“It was easily the most horrific day of both our lives,” Kristie says.

Brett and Kristie are not the only parents to have lived through such a terrifying ordeal. Over the past three years in Australia, there have been seven deaths caused by leaving a child in a hot car – and in every case, the parent responsible was unaware of what they had done until it was too late.

In America, the problem is just as common. Mary Parkes, mother to two adopted boys, discovered she’d left her son, Juan, in a hot car for eight hours after forgetting to drop him to day care. Mary only realised her mistake when got a call from one of her son’s teachers saying they had missed him at school that day.

“That was my first indication that anything was wrong,” Mary told 60 Minutes. 

“I said to her, “He was at school.” And she said, “No, he wasn’t at school.” And I took off running for the car.”

When she discovered her son’s body, Mary Parkes was forced to make the phone call that no parent should ever have to make – to inform her husband, Geoff, of Juan’s death.

“She goes something like, ‘I think I’ve killed our son’,” Geoff recalls.

“And I said, “What? What?” And she goes, “Just come right away.”

Mary is still in disbelief about the incident.

“To me, it was it was so surreal. How… I mean, how could it happen? How could you forget something that you love so much?”

It’s the question that plagues every parent in Mary Parkes’ position. How could something like this happen?

And yet, according to Professor Matt Mundy, a memory expert at Melbourne’s Monash University, lapses in short-term memory are extremely common.

As Professor Mundy told 60 Minutes, leaving a child in a car is not a result of negligence. Rather, when distracted, short-term memory can be blanked out. Somebody who’s distracted operates on ‘autopilot’, and will often fill in their actions while in that state with prior memories from similar occasions. Professor Mundy refers to the experience of parents like Mary Parkes and Brett Cavaliero as a ‘fatal distraction’.

The distinction between negligence and genuine mistake is an important one, given that negligent manslaughter carries with it a maximum prison sentence of 20 years. Both Mary Parkes and Brett Cavaliero were under criminal investigations for their actions.

Due to a growing acceptance of the idea of ‘fatal distraction’, the charges against both bereaved parents were eventually dropped. Increasingly, the response to such tragedies is compassion, rather than criminal charges, for the devastated parents.

For Brett and Kristie Cavaliero, the pain of losing Sophia will never be erased. They’ve dedicated themselves to preventing similar deaths, establishing a foundation in their daughter’s name and creating an app that activates an alarm when a driver leaves their car with their child still inside it. They’ve also successfully lobbied for thousands of daycare centres across America to call parents if their children aren’t delivered as expected.

Hopefully the tragic loss of Sophia, Juan and other babies like them will serve an important purpose – to remind parents of the devastating risks of ‘fatal distraction’.

Have you ever forgotten about your child, even if just for a moment? Do you think that those who do should face criminal charges?

60 Minutes aired at 8.30 on Sunday night. 

Read more:

That moment that changes a life. When a Dad realises he left his baby in the backseat of the car.

Rescuers who pulled unconscious baby from car heard a ‘mysterious’ female voice urging them to help.

“The day I left my baby in the car.”