A father and his son were shot dead while seated in their car in Alberton, south of Johannesburg, on Tuesday afternoon.
Police spokesperson Capt Mavela Masondo said the shooting happened at about 1pm.
Masondo said the two were seated in a BMW when a white Hyundai i10 stopped next to it and opened fire.
The father, aged 53, and his son, 27, were declared dead on the scene.
The motive for the murders is unknown.
Masondo said a manhunt had been launched for the suspects.
Anyone with the information can call the nearest police station or crime stop on 0860 010 111.
