The 34-year-old, identified by local media as Joseph Versace, was found dead at the scene in Gnangara on Thursday afternoon following reports of gunshots.
Police Commissioner Col Blanch said detectives were speaking to multiple witnesses but were yet to place a suspect in custody.
Investigators believe the matter is linked to outlaw motorcycle gangs but are yet to establish the reason behind the shooting.
Mr Blanch said a taskforce had been established and officers had already raided four properties.
"This is something that I will not tolerate as commissioner in Western Australia - cold-blooded killings, public acts of violence," he told reporters on Friday.
"We have activated the gang crime squad. They will be executing and have executed a number of search warrants already."
Mr Blanch declined to confirm the victim's identity but said he was known to police and was believed to have been associated with bikie gangs.
He downplayed the threat to the public, describing it as a "targeted attack over an incident or an issue that we are looking into".
Any retaliatory attacks would be met with a strong police response, he warned.
"If you are in an outlaw motorcycle gang hierarchy, you also have an obligation to make sure your members and your associates behave themselves in the public domain," Mr Blanch said.
"If you get out of line, if you start doing things like this, the gang crime squad will come for you."
Police are seeking CCTV, dashcam or mobile phone vision of any people or vehicles in the Gnangara area between 1pm and 4.30pm on Thursday.
They are yet to disclose the type of firearm used or how many times the victim was shot.
Authorities have cracked down on bikie-related crime in WA in recent years.
It was spurred in part by the slaying of senior Rebels bikie Nick Martin, who was gunned down from long range by a hired sniper at a Perth drag racing event in December 2020.
The gunman, a former soldier who cannot be named for legal reasons, pleaded guilty to Martin's murder last year and was jailed for at least 18 years.
Former Rebels bikie David Pye is accused of organising and paying for Martin's killing. He has been charged with murder and other offences but is yet to enter pleas.
Police Minister Paul Papalia said the McGowan government was targeting bikies with anti-consorting legislation and a rewriting of gun laws.
"We are going to be focused on disrupting, dismantling and making this the least receptive place in the country for that type of behaviour," he said.
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