A tight-knit community is reeling after a kindergarten student and her baby brother were killed when a SUV collided with a pram shortly after school pick-up.

The girl and her brother have been identified as Katherine, 5, and Harry, aged 14 months – the only two children of 33-year-old mother Sok Ram.

The children were struck by the vehicle while crossing a street with their mother in Cabramatta, in Sydney’s south-west, about 3.15pm on Wednesday.

Katherine was in her first year of kindergarten and had just been picked up after receiving an award, according to an online fundraiser on the family’s behalf.

Outside the family’s Cabramatta home on Thursday, Ram and the children’s father, Vundy Tha, said they “cannot believe” their children are gone.

“Why did my kids die? I hope [the car] would hit me, not my baby,” Ram said.

Ram, 33, said she was pushing Harry in the pram and crossing the road with Katherine when they were hit by a car she had thought slowed down to let them cross.

The man behind the GoFundMe for the family, Patrick Te, said the children’s lives were taken in a “split second”.

“As they were crossing the road together, heading back to the car, an oncoming vehicle suddenly struck both Katherine and the pram where Harry was sitting,” he said.

“A mother not only lost a child — she lost both of her children, her only two children.”

The GoFundMe fundraiser had raised more than $65,000 in donations by late on Thursday morning.

The children’s heartbroken parents, Vundy Tha and Sok Ram, say they forgive the driver. Photo: Seven Network screenshot

Paramedics treated the children at the scene and they were taken to hospital in a critical condition but died shortly after, police said.

Ram was treated for minor injuries at the scene.

A 56-year-old man who was driving the car was uninjured and taken to hospital for mandatory testing.

Ram said her daughter was a generous child who did not want gifts but just wanted to be surrounded by her family.

“I gave my kids everything, the big one (Katherine) she said ‘Mummy and family more important than iPad’,” she said, as she was comforted by her husband and a friend.

She said her daughter had dreams of growing up to become an artist or a teacher while her toddler son — who had just learned how to walk — loved kicking a small soccer ball around.

The children’s father Vun Dy Tha, 42, was at work when his wife called him and told him of the accident that claimed his children’s lives.

“In my mind, I thought it was only one kid but it was both of them because my son, the little one, always wants to come with us in the pram,” he told AAP.

“They are beautiful kids.”

He explained the car had suddenly stopped, giving Ram the impression she could cross the street safely, but then it struck them with children trapped underneath.

On Thursday, Ram said she forgave him, but pleaded for other drivers to “please look, be careful before you go”.

Tha also said he forgave the driver, because blaming him would not bring his children back.

“I would like to say thank you for everyone … I wasn’t there, thank you to everyone,” he said.

“Even the driver, I forgive him already.

“Nothing can change, you know? Nothing can change. I couldn’t get my kid back.”

NSW Police’s crash investigation team is looking into how the incident happened.

NSW Premier Chris Minns said it was a terrible event and everyone was heartbroken by the loss of the two young lives.

“This is one of those tragedies that hit the community incredibly hard,” he said.

Police said several witnesses had rushed to the aid of the critically injured children.

”The community involved here this afternoon was, I can only say, phenomenal,” Acting Superintendent Timothy Calman said.

”We’ve had a number of motorists that actually stopped and collectively have moved the vehicle onto its side, tipped the car over in order to get one of the children from underneath the vehicle, and other bystanders have assisted with CPR.”

Minns said he wasn’t surprised to hear the good Samaritans had tried to save the children’s lives with their “heroic efforts”.

-with AAP