Former Comancheros bikie boss Mahmoud "Mick" Hawi is on life support and not expected to survive after being shot outside a gym in Sydney's south on Thursday.
Just after midday police attended a carpark area in West Botany Road after receiving information a man had been shot near a Fitness First gym in Rockdale.
Police found a man suffering a gunshot wound and he was taken to St George Hospital in a serious condition.
NSW Police said Thursday's gunman appeared to have fled in a vehicle which was last seen on nearby Lindsay Street.
Hawi has served time in jail over his role in the killing of Hells Angels associate Anthony Zervas, who was bashed with a bollard during a violent brawl between the rival clubs at Sydney Airport in 2009.
NSW Police have cordoned off the carpark in front of the gym's entrance where a black four-wheel drive with apparent bullet holes is parked.
"A crime scene has been established and investigations are continuing," police said in a statement.