Three people are in custody in connection with the shooting in which the well-known South African racer, Robert Wolk, was killed on Wednesday in Kempton Park.
The Srebela police confirmed that one person was arrested on Friday, while two more people were arrested on Saturday morning.
Maroela Media reported earlier that Wolk (41) was on his way to Cape Town to participate in a race when he was involved in a minor car accident at the corner of Camwood Street and Portland Road in Esther Park.
Disturbing footage, which is circulating widely on social media, shows how Wolk took photos of the accident before the driver of the other vehicle climbed out. It can then be seen how Wolk ran away and was shot from behind and fell to the ground.
The Gauteng government expressed its condolences to Wolk's family, friends, and the motorsport community on Sunday.
"The tragic and violent death of Robert Wolk, a true ambassador for South African motorsport, has deeply shocked our province. Bullying and senseless violence have no place in our society," said Panyaza Lesufi, Gauteng Premier.
He also welcomed the police's actions after the shooting.
"We are grateful for the quick and decisive reaction of the police to arrest the suspects connected to this tragedy, and we trust that the full force of the law will ensure that justice is served," he said.
Wolk's career in motorsport spanned almost three decades, during which he won numerous national titles.
He also won successive South African GTC championships and was also celebrated at the Simola Hillclimb.
The Gauteng government described him as an outstanding sportsman.
"Our province mourns with the Wolk family during this devastating time. May his legacy continue on the racetrack, and may his soul rest in eternal peace."