From an article I found:
A Johannesburg motorist risked his life on Sunday to rescue a metro police officer held at gunpoint on the M2 East near Cleveland.
Chief Superintendent Wayne Minnaar said the officer was setting up his speed camera early on Sunday morning when he was approached by two men, in their twenties.
"One pointed a gun at him and demanded that the officer give them his weapon," said Minnaar.
The officer refused, grabbed the firearm from the gunman and started wrestling with him.
It was at that point that a 35-year-old motorist stopped to help.
He got out of his car, pointed his Colt .45 firearm at the gunman and ordered him to drop his gun.
The gunman refused and the motorist shot him twice, wounding him in the hip, said Minnaar.
The two men ran away over the highway and were later found and arrested in the Cleveland area by Ekurhuleni metro police.
"We would like to thank the man for this brave action. He has asked to remain anonymous. He was very, very courageous to stop and help an officer in trouble," said Minnaar.