Heartbreaking CCTV footage shows final moments before stroller rolled onto tracks killing child and ‘heroic’ father

Heartbreaking footage shows the moments before a pram rolled onto train tracks at a station in Sydney.

The pram, which was occupied by twin girls, rolled onto the track as a train was approaching the platform at Carlton Station in Sydney.

The children's father leapt onto the track in a last ditch effort to save the two girls.

Tragically, the father and one of the twins was killed by the approaching train, while one of the twins survived.

The twins' mother, who was not physically harmed, watch the horrifying incident unfold from the platform.

Both the surviving girl and the 39-year-old mom were rushed to St George Hospital.

In the footage, the family can be seen heading out on an outing before the tragedy struck.

Images show the dad on the platform with the pram in front of him facing towards the tracks.

CCTV images from before the horrific accident. (Nine News)

Just seven minutes before the accident, the family were seen walking along passing grocery stores with the father in charge of the pram, while the mom was pulling a shopping trolley.

New South Wales police superintendent Paul Dunstan praised the father, saying: “He’s just gone into parent mode and tried to save his two young daughters.

“In doing so, it’s cost him his life. But it was an incredibly brave and heroic act.”

He also said that the mom is being looked after by loved ones, saying: “She’s being well supported by her friends and family but she’s clearly in a state of shock and struggling with what’s happened today."

NSW state premier Chris Minns also paid tribute to the dad.

“He gave his own life to try and save his children," said Minns.

Emergency services at the scene. (7NEWS Australia)

“It’s a very confronting and sad day for the St George community and for that family from the Kogarah area.”

The train had been approaching the platform on the way from Cronulla to Bondi Junction, and had not been due to stop at the station.

Sydney Trains chief executive Matt Longland said that the train was being driven by two 'experienced crew'.

He said: “It was approaching the station with caution. That’s how our drivers are instructed to drive in order that they can make sure that there’s no incidents on the platform.

“These sorts of incidents are incredibly rare, but clearly the outcomes are absolutely tragic.”

An investigation has now been launched into the tragic circumstances.

This will include examining the speed of the train and how the pram ended up on the tracks.