The driver who allegedly struck and killed a teenager in a hit-and-run in Sydney's south-west returned to the scene 11 minutes later before fleeing again, police say.
Police are still searching for the driver of the white ute who struck Natasha Gadd on Henry Lawson Drive, Milperra, at 4.30am on Sunday before driving away.
Paramedics were unable to revive the the 19-year-old, who was on her way home with two friends, and who died at the scene.
Police on Monday said CCTV footage had now revealed the driver of the ute returned to the crash scene and would have been fully aware of what had occurred.
"They do know because we do have CCTV footage, which we will be releasing and the vehicle went back past the area approximately 11 minutes after the crash so they would know that they hit the girl and left her there," crash investigation unit's Detective Inspector Katie Orr said.
"It's callous, it's tragic, she was a young girl, she's 19, she's a daughter, she's a sister, she's a friend and to leave her there to die is very tragic for the family."
Detective Inspector Orr said the ute had a purpose-built refrigeration unit in the rear tray and had also lost side mirror, which police hope will help identify the vehicle.
She said the investigation was in its infancy but said officers now had the CCTV footage as well as statements from witnesses.
"If you are the driver, I would urge you attend your nearest police station and hand yourself in," Detective Inspector Orr said.
"We do have CCTV images and footage of the incident and there are a number of witnesses so before we come knocking on your door I would urge you to attend your local police station."
Ms Gadd's family have described her as fun, loving and energetic and have been left devastated by her death.
She was also a promising soccer player.
In an interview with Channel Nine on Sunday, her mother Charmain praised her dedication.
"I was always proud of her. Anything that she put her mind to, she could do," she said.
"Put yourself in my shoes. How would it feel to wake up this morning to that news?" she added.
"My baby is never coming home."
Friends and family have posted a number of posts on Facebook praising Ms Gadd for her bubbly, outgoing personality.
"Accidents happen, but when you take off, that's no accident," Ms Gadd's aunt Mel told Channel Nine.
Anyone with information is urged to contact Crime Stoppers on 1800 333 000.