No arrests have been made but police said two suspects were seen running from the scene.
Detective Superintendent Gordon Allison of Operation Trident, which tackles gang-related crime, said: "As far as we're concerned, this looks like a tragic case of mistaken identity. They have parked just opposite a shop - we believe they were going to go into the shop and make a couple of purchases and then they were going to go home.
"They have been approached by the two suspects, a short conversation has taken place and as a result of that, three shots were fired into the vehicle, resulting in the fatal injury of the victim."
Officers are still trying to find a motive for the shooting. One of the two suspects is black, police said, while the second is light-skinned, possibly of Asian or Turkish appearance.
They were seen running away from Hindrey Road after the shooting towards the nearby Pembury Estate. Police are speaking to witnesses, checking CCTV and carrying out forensic examinations as part of their investigation.