By Nick Dole, ABC
Investigators are studying CCTV vision from Carlton train station to determine how a pram carrying twin two-year-old girls was able to roll onto the tracks.
One of the girls was killed when she was hit by the train on Sunday afternoon, along with her 40-year-old father who jumped onto the tracks in an attempt to rescue his daughters.
Their bodies were removed from the scene last night.
His actions have been described as "incredibly brave and heroic".
The other girl was found crying under the train and was taken to hospital for checks, along with her 39-year-old mother who watched the horrific scene unfold.
Investigators are piecing together video of the family of four making their way down the lifts and onto the platform.
NSW police Superintendent Paul Dunstan said they had just got out of the lift and the parents had taken their hands off the pram for a "very, very short period of time".
"Whether it's a gust of wind, we're not quite sure, but it appears that the pram has instantly started to roll in the direction of the train lines."
On Saturday, Sydney experienced severe winds which affected services at the nearby airport but conditions had eased by early Sunday afternoon.
However, investigators will still try to assess whether a wind gust could have generated enough force to send the pram rolling onto the tracks.
Sydney Trains chief executive Matt Longland said these kinds of incidents were "incredibly rare" and they were working closely with police to build a picture of how the incident unfolded, including train speed.
He said the train involved was not due to stop at that station and it was slowing down in line with protocol.
"It was heading towards Bondi Junction, it was approaching the station with caution," he said.
"That's how our drivers are instructed to drive in order that they can make sure that there's no incidents on the platform. So I can't comment on the speed it was operating at."
The National Rail Safety Regulator had been informed, he said.
According to Dunstan, the "train did stop at a short distance from the end of the platform".
Government will consider safety changes, if needed
The NSW coroner will also assess any potential deficiencies in safety on the platform.
Images from the station show passengers exit the lifts parallel to the railway tracks, not immediately facing them.
Premier Chris Minns said it was a "very confronting and sad day" and it was "too early" to say whether safety changes were warranted and that he was waiting for a clearer picture to emerge.
"I don't want to close the door on any potential changes we could potentially make to ensure people are safe, particularly children," he said.
Asked whether his government would consider installing safety screens, similar to those on metro stations, he said he would need to take advice.
"I can't promise that this afternoon without knowing how it would be achieved and what it would involve.
"But obviously, we'll work with New South Wales trains follow the New South Wales Police inquiry, and if changes need to be made, we'll make them."
Train crew offered support
Sydney Trains said the two crew members on the train were being offered support.
According to Longland, both were based at Central station.
"They're two of our more experienced crew who are obviously trained in first aid," he said.
"But clearly, the nature of this incident was very confronting.
"Both of those crew are being supported by Sydney Trains. We're working through post-incident support for them, in addition to our member of staff at Carlton train station."
- This story was first published by the ABC