Australian mother Rebecca Olsen and her son die in car crash in US after pickup truck crashes into their Tesla

An Australian mother and her son have died in a freak car accident in the US.

A white Toyota Tacoma pickup truck is believed to have veered onto the wrong side of Highway 85 in San Jose, California, before colliding with a Tesla carrying Rebecca Olsen, 47, and her son Charlie, 14, around 3:40 p.m. Monday.

The pair were killed in the horrific collision.

According to the California Highway Patrol, the freeway was closed due to the collision between the pair’s Tesla and the Toyota Tacoma.

Ms Olsen’s ex-husband and Charlie’s father, Cameron Olsen, said there was a void in his life that “could never be filled”.

He remembered his ex-wife as a loving mother. The couple met in Australia when they were 20. According to Olsen, they were the best “co-parents” together.

The trio moved to Silicon Valley 12 years ago, where Olsen sought work at a local tech company.

“Rebecca was an incredible mother: loving and deeply committed to our son’s future,” he wrote in a social media post.

Charlie Olsen, 14, and mother Rebecca Olsen, 47, (above) died in a head-on collision in the US

The horrific crash involved a large pickup truck driving the wrong way colliding with the pair’s Tesla.

“She believed in the power of education and was passionate about travel. She always encouraged Charlie to broaden his horizons.”

Charlie was born in the UK and has visited more than 30 countries, his father said.

“Charlie was a bright spot in our lives. He had an insatiable curiosity and passion for the world around him,” Olsen said.

‘Whether he was traveling to new places, immersing himself in a good book, learning yet another language, or solving complex math problems, learning brought him joy.

‘He was my best friend, my traveling companion and the only person with whom I truly felt at home.

“I want my son back beyond belief.”

Mr. Olsen left a link for donations to Summit Tahoma High School so that other children’s children could also enjoy the field trips his son was so excited about.

“Many of you have asked how we can best honor their lives and legacies…if you are inclined to donate in memory of Charlie and Rebecca, please consider directing your gift to Summit Tahoma High School,” he wrote, with a link to the donation site.

Mr Olsen told news.com.au his son had passed an exam to jump forward a year in maths, but he only found out after his son had passed.

He last saw his son three days before the accident, on Friday, and said he was “super happy.”

“Charlie was remarkable. Spoke multiple languages. Knew political systems inside and out. Had been to 7 continents by the age of 13,” Olsen said.

He also said that the days since the accident have been passing slowly and that he is grieving his loss.

“I feel like every minute is an hour and every hour is a day and every day is a week. It’s a blur,” he said.

“I officially identified Charlie today at the coroner’s office (via photo). He was severely damaged in the crash and I haven’t stopped crying since.”

The crash closed three lanes of Highway 85 on Monday and sent a Florida man to the hospital

According to US media, the California Highway Patrol had received reports of a white Toyota Tacoma driving the wrong way on Highway 85 on Monday before the collision.

According to CBS News, the driver of the Toyota has been identified as Duncan McQuarrie of Orlando, Florida.

According to reports, he was seriously injured and taken to hospital.

No charges have been filed.