A video shot in the Jaguar believed to be that of former racing driver Andrew Turnbull shows the car travelling at a speed of 260km/h.
According to Netwerk24, the video was taken and shared on WhatsApp by Turnbull's friend and passenger, Ryan Byrne, 20, on Sunday.
Turnbull's Jaguar was involved in a high-speed collision on the R72 near Port Alfred in the direction of Kenton-On-Sea on Sunday afternoon, Dispatch Live reported.
Byrne died on the scene, according to Netwerk24, while Turnbull died in hospital on Monday.
The driver of a Mercedes-Benz that Turnbull crashed into was also killed, police spokesperson Captain Mali Govender said.
Govender said the collision took place at around 14:30 about 10km outside Port Alfred in the direction of Port Elizabeth.
The video shows the car travelling at high speed, with a tattoo on the driver's left arm being identical to that of Turnbull.
On Monday morning, Turnbull's mother Martha posted on his Facebook page: "Andrew, our only son and brother to Lindy, passed away in the early hours of [Monday] morning in PE [Port Elizabeth] due to serious injuries from a car accident. His friend Ryan Byrne died at the scene. Please, I'm am begging everyone to please give us time to mourn and to stop the horrible stuff that is being posted on [Facebook]. We are heartbroken."
According to Netwerk24, Byrne was a flight school student at the 43 Air School in Port Alfred.
In another video, posted by Turnbull on his Facebook page about six months ago, a speedometer is shown to increase to just under 260km/h on a public road. Turnbull wrote: "Nothing better than a vehicle that can safely cruise at decent speeds in comfort."
Charged with assaulting girlfriend
Turnbull was out on bail after being charged with assaulting his former girlfriend Chere Gray.
Times Live reported last year that, in a video, Turnbull could be seen pinning Gray against a wall, then tossing her aside as the person filming the video is heard pleading: "Andrew, please calm down."
The incident reportedly happened in August.
Turnbull reportedly told the Randburg Magistrate's Court in October last year that he grabbed her by the collar and spoke harshly after she had a "relapse" and went on a shopping spree with his credit card.
Turnbull was also accused of drug and ammunition possession in a separate case. After a successful bail application he was released on R5 000 bail.
On Monday, Gray posted on Facebook that she had forgiven Turnbull. "There was once a time when I loved you with all of me. Regardless of what has transpired, I forgave you a long time ago... May you rest peacefully now."