The victim, who lives on Sentrust Street, returned to her Crystal Park home from Daveyton, at around 1.55am.
Crystal Park SAPS media liaison officer Tryna Maritz said the victim exited her car to open the gate leading into her property.
As she was doing this, two men arrived in a white Opel Corsa.
One of the hijackers was armed with a pistol.
“She started screaming and the police members in the charge office heard her,” said Maritz.
Maritz said the officers ran to the scene and one of them fired three warning shots.
One of the suspects fled in the hijacked BMW while the other fled in the Opel.
Police gave a lookout for the stolen vehicle, after which Putfontein SAPS spotted the car on Geldenhuys Road.
A chase ensued but ended when the hijacker wrapped the car around a street pole, in Esselen Park, Kempton Park.
No arrests have been made.
The woman was not injured in the hijacking.
A case of hijacking has been opened at the Crystal Park Police Station.
