Police spokesperson Brigadier Sabata Mokgwabone said the man was arrested on Saturday in Soshanguve, north of Pretoria.
"The arrest came after a manhunt was launched following an incident in which three suspects allegedly shot and killed Constable Samuel Hlongwane, 35, and robbed his friend of his BMW at about 9pm in Letlhabile near Brits on Friday, [June 2]," he said.
He said the off-duty constable was walking along Letlhabile's main road when his friend, driving in a BMW, stopped for a chat.
"They were still chatting when two unknown males confronted and pointed them with firearms. Although the constable managed to pull out his service firearm, the suspects shot him on the left arm and on the head. Upon firing back and before he died on the scene, Constable Hlongwane allegedly shot one of the suspects on the left arm and lower body."
He said it was alleged that the third suspect came with a getaway car, picked the wounded suspect and left him at Letlhabile clinic, while the other suspect drove the BMW belonging to the constable's friend, who was unhurt.
They also took the constable's service firearm. Taxi operators became aware of the incident and followed the suspects' car until at the clinic where they allegedly assaulted the wounded suspect until he died.
The police managed to recover the robbed BMW, as well as the suspects' getaway car on Saturday.
"The search continues for the other suspect while the arrested one is expected to appear in the Brits Magistrate's Court today [Monday] charges of car hijacking and murder."