Emergency services were called to North Rocks Road in Carlingford, in Sydney's northwest, shortly after 7am on Wednesday following reports of a shooting.
Officers found the man, aged in his 30s, with significant wounds from multiple gunshots inside a car.
He was unable to be revived and died at the scene.
"We know there were multiple shots, but we are still processing the crime scene," NSW Police Acting Superintendent Michael Marinello told reporters.
The victim was known to police and the attack did not appear to be random, police said, with investigators probing potential organised crime links.
"It does seem to be a very brazen attack," Acting Supt Marinello said.
"We believe this is an isolated incident and that there is no ongoing risk to the public.
"We will be looking into connections that the man may have had with other people within the community."
One of the lines of inquiry for police were reports the shooting may have occurred up to two hours before emergency services arrived at the scene.
"That's one of our preliminary inquiries that we are looking into," Acting Supt Marinello said.
"There's obviously a lot of CCTV footage that we'll go through as a result of this."
Several witnesses are assisting police, including those inside a home near where the car was at the time of the shooting.
A heavy police presence including forensics officers remained on the scene as of midday, with North Rocks Road closed and the public urged to avoid the area.
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