CCTV footage shows the terrifying moment the buggy veers to the right and rolls over the edge of the platform, after the mum lets go of the handles to retrieve a dropped shoe.
The mother follows the buggy onto the tracks and two other passengers jump down from the opposite platform to help rescue the two-year-old boy.
The mother is then seen cradling the boy as the other passengers scramble to lift her belongings off the track and a train travelling in the opposite direction arrives at the station.
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David Phillips was one of the bystanders who was about to board a train at Camberwell station in Melbourne, Australia, on Saturday (September 13), when he saw the buggy go over the edge.
"Without hesitation I just jumped into the pit to try to help out, do the best I could," he told 9NEWS.
"She was distressed. The kid was crying. Quite a few other people were concerned."
The boy, who has not been named, was taken to hospital after suffering 'minor facial injuries' in the fall.
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