Cops are now investigating if the car's autopilot mode was a "contributing factor" in the accident.

Another man, who was aiding the driver of the semi out of the wreck was also seriously injured when he was hit by the Tesla.

On Thursday, the California Highway Patrol (CHP) said the car's autopilot "was engaged" before the smash, but later added saying "no final determination made."

Hendrickson previously posted on social media about his car, including boasting several times about driving the car with no hands.

A video on his Instagram account showed him sitting in the driver's seat without touching the wheel or pressing down on the pedals as the vehicle drove through freeway traffic.

“Best carpool buddy possible even takes the boring traffic for me,” he wrote alongside the clip.

"Coming home from LA after work, thank god, self-drive,” said a comment on another, adding, “Best car ever!”

The dad's Facebook also features a video while driving on autopilot mode, saying: "Don't worry. I am on autopilot."

The Tesla Club-SoCal, which Hendrickson is believed to be a member of, is planning to organise a remembrance drive in his memory.

“Every time we spoke to him, he would light up talking about his kids and loved his Tesla,” the club posted on Instagram.

“He was truly an amazing human being and will be missed!”