Police are examining CCTV footage in a bid to identify a gang who held a gun to an eight-year-old boy's head to steal his mother's car.
The stolen BMW was later found abandoned nearby
The group struck at the Red Lion Filling Station on Stockport Road, Cheadle, Greater Manchester, on Monday.
The child was in the blue BMW X5 as his mother vacuumed the car when three or four men approached.
They pointed the weapon to his head and dragged him out before driving off. The car was found abandoned in Fallowfield.
Police discovered the car in Ladybarn Lane, Ladybarn, where it had collided with a bus.
Three men, one of whom was seen to be limping, were seen running from the car after it was abandoned.
A Greater Manchester Police spokeswoman said: "The eight-year-old boy was uninjured but has been left extremely shaken by what happened."
He is currently being treated for cancer, police said.
Officers are currently examining CCTV footage seized from the garage in a bid to trace the gang.
The woman, from Gatley, had been on her way to pick up a child from school when she stopped at the garage on Monday afternoon.
The gang, who were armed with a handgun, pounced as she was vacuuming the car on the forecourt.
Local resident Jack Goodwin, who witnessed the robbery, said the woman was under the bonnet of the car when the attack took place.
He told BBC News: "Obviously (they) must have grabbed the keys off her, jumped in the car, reversed and then drove out - still with the bonnet up - and sped off down the road.
"The mother and the little boy were very distressed and upset."
Police are appealing for anyone who saw the incident, which happened at about 1510 GMT, or the car, to contact them.