The story you didn't hear about the child filmed riding on a car roof rack.

This week we all sat aghast as footage was shared of a young boy riding on top of a car for several kilometres through the streets of Perth.

Now, the mother of the four-year-old boy has spoken out, through a representative, to explain how the “freakish event” happened.

The mum, who only wants to be known as Erica, had buckled her son into the backseat of the car and didn’t realise that her son had unbuckled his seatbelt and climbed atop the roof when she took off, family spokesman Gerry Georgatos said.

Georgatos, who works for the National Indigenous Critical Response Service, explained to the media that Erica had no indication that her son wasn’t in the backseat and was “blindsided” when she found him on the roof rack, ABC reports.

"She had thought the three were all buckled up. When she had her first inclination (something was wrong) she did look in the back, she pulled over and she stopped."

According to witnesses, the boy, who reportedly has autism, was on the roof of the car for around 10 minutes - and in that time the car had travelled roads including Tonkin Highway, which has a 100km/h speed limit.

Police were called by fellow motorists who noticed the boy and they soon intercepted her, finding three children in the backseat, one of whom was unrestrained.

They charged the 36-year-old mum with dangerous driving and gave her summons to appear in court at a later date.

Georgatos has called for those charges to be dropped, claiming the woman's driving wasn't dangerous.

"I'd like to see the charge removed, I don't see there is any reason for dangerous driving because there was no presumption of the mother dangerously driving," he said.

"This is an extraordinary event, it was a freakish event, it was something unforeseen."

However, he said now what was troubling the family - as much as the "shellshock" of knowing how easily the boys could have fallen and been injured - was the abuse they faced online.

"[The comments] are disturbing and they are cruel, they are insensitive," Georgatos said.

"That also compounds trauma to be exposed to such public brutality."

Meanwhile, Nine News reports locals have claimed on social media that the mum has driven with her son atop the roof before, telling people that "he likes it".

Georgatos' comments refute this.

"What happened was inadvertent. It was without knowledge. They're shell shocked. They're grieving at what could have happened," he told Nine News.