Mrs Bernadette Moran, wife of well-known Letterkenny surgeon Kevin Moran, was stopped at traffic lights when the horrific attack happened at Mountjoy Square.
The attacker pulled 37 year old Mrs Moran from the car not knowing that her 10 year old son was in the back.
The thief drove off but luckily stalled the car a few yards away from the robbery.
Mrs Moran then managed to grab her son from the car as the thief got the car started again and sped away.
Neither Mrs Moran, who owns a crèche on the outskirts of Letterkenny, nor her son were hurt following the ordeal but were seriously traumatised.
The car was later discovered abandoned by Gardai a short distance away from the scene of the crime.
Gardai are carrying out forensic tests on the car and are also studying CCTV footage for the area in a bid to identify the attacker.
Mrs Moran declined to comment when asked about their ordeal.