Witnesses at the scene rushed to the family’s aid after the collision, with one describing how he just held the little boy as he slipped out of consciousness.
“We were trying as hard as we could to keep the little boy alive and awake but he went unconscious on us. There was nothing we could do,” the witness told The Daily Telegraph.
“There was also a nurse who just happened to be driving by and she tried her hardest.”
Emergency services tried to revive him at the scene before he was rushed to hospital but he was pronounced dead on arrival.
Tributes have begun pouring in for the family, and the mother who was a beloved occupational therapist who worked tirelessly for her community.
“Can’t believe this has happened. May my amazing aunty Julie and cute little cousin Hudson Rest In Peace. I hope to see you soon little Sienna,” Ms Bullock’s niece Chelsea Andrews wrote online.
“Today we all lost an amazing lady who helped our community so much and also sadly lost one of her twins while her little girl fights for her life,” she posted.
“Julie Bullock you did so much for Jacob being his Occupational Therapist for all that time. I know you’ll be in heaven with your little man. We’ll pray for your little princess. My condolences go to your family.”
“R.I.P Julie Bullock, so sad to hear of you and Hudson today. My heart breaks. A vivacious outgoing beautiful girl taken too soon. Will miss you xx”, wrote Toni Millevoi on Facebook.
Wollondilly Anglican School headmaster Stuart Quamby told the Daily Telegraph that the small community had been rocked by the devastating news.
"The family are well known and well-loved, not just in the college community but in the wider community as well. It is going to be tough because there is will be a lot of hurt in the community because we are a small community out here, it is a country community.”
A gofundme page has been set up to help the family and has already raised over $13,000.