Police are still no closer to establishing why a car crossed a New South Wales highway, killing a mother and one of her twin children on their way to school yesterday morning.
A seven-year-old girl remains in a stable condition in hospital after the crash which claimed the life of her twin brother and her mother.
Sienna Bullock was travelling in the car with her brother, Hudson, and her 49-year-old mother Julie when they collided head-on with a Holden Astra which crossed onto the wrong side of the highway at Wilton on their way to school.
Ms Bullock was killed on impact, while Hudson died shortly after the crash.
In a shocking twist, the driver who crashed into them, Tina Vibert, 49, is also the mother of twins who went to the same school.
Flags flew at half-mast at Wollondilly Anglican College today, where the headmaster said the tragedy has resonated deeply with the school community.
"Nobody walks here and nobody drives here, they all travel by bus or by car and so it resonates with everyone. ‘That could have been me or it could have been my kids’," Dr Stuart Quarmby told 9NEWS.
Sienna is recovering at the Children’s Hospital at Westmead, where her father, Darren, is keeping a bedside vigil.
"He is obviously deeply affected he is sitting beside the remaining part of his family which is his little girl. He is praying for her and looking after her," he said.
Police are trying to determine exactly what caused the Astra to veer over the median strip and onto the wrong side of the road yesterday morning.
Ms Vibert remains in a serious condition at Liverpool Hospital and is not yet well enough to talk to police.
Witnesses said the car “seemed to pick up speed” after crossing over onto the wrong side of the road.
Friends have paid tribute to the mother and son, expressing their shock and heartbreak at a seemingly normal Tuesday morning which ended in tragedy.
“A vivacious, outgoing, beautiful girl taken too soon,” Toni Millevoi wrote on Facebook.
Inspector Mick Pearsall yesterday described the crash as “absolutely devastating”.
“All accidents are difficult but when there are young children involved it affects everyone and we are no different,” he said.
Friends have set up a GoFundMe page for the Bullock family, which has so far raised $21,415 of its $25,000 goal in just 20 hours.