The footage shows the three-metre great white approaching 23-year-old Kai McKenzie at North Shore Beach at Port Macquarie on the state’s Mid-North Coast before he lost his right leg in the mauling last Tuesday.
Footage of the attack showing McKenzie desperately attempting to escape the shark has since been leaked.
Police confirmed the internal investigation is underway.
“NSW Police are aware of a video circulating online and have commenced an investigation into how the video came to be released,” police said.
“The NSWPF does not tolerate this kind of conduct and will take appropriate action pending the outcome of the investigation.”
A man who was on beach with his dog rushed to help McKenzie and used his dog’s leash as a makeshift tourniquet to stop the bleeding on the surfer’s leg.
After the ordeal, the surfer was treated by paramedics and flown to John Hunter Hospital in Newcastle for treatment.
An online fundraiser has raised more than $174,000 to support McKenzie’s rehabilitation and recovery as of early today.