The brazen shooting murder of notorious former bikie boss Mahmoud "Mick" Hawi as he sat in the driver's seat of a luxury 4WD is feared to spark a new round of Sydney underworld revenge attacks.
The ex-leader of the Comancheros was shot multiple times outside a Fitness First gym in Rockdale in Sydney's south about midday on Thursday and later died in St George Hospital.
His 4WD was peppered with at least half a dozen bullets in the underworld hit.
Two men in dark clothing were captured on CCTV fleeing the scene after the attack. Witnesses identified a man wearing a balaclava as the gunman.
Shortly afterwards, a Mercedes Benz station wagon was set alight on a nearby street.
Police described the daylight murder of the 37-year-old as a "serious, brutal and callous".
"This was a planned and targeted attack," Assistant Commissioner Mal Lanyon told reporters.
He said detectives are investigating Mr Hawi's underworld links and who may wanted him dead, while full resources are also being deployed to prevent retribution for the murder.
"It's essential, when we believe there could be links to organised crime, that we take action to prevent that," Mr Lanyon said.
Hawi served time in prison for his role in the killing of Hells Angels associate Anthony Zervas who was bashed with a bollard during a brawl between the rival clubs at Sydney Airport in 2009.