The man was fatally shot by police in a laneway off Whitlock Street in South Kalgoorlie, 600km east of Perth, just after midday on Friday.
Assistant Commissioner Darryl Gaunt said the man was armed with a handgun and had been given numerous warnings - which he did not heed - as he moved towards police.
"The gentleman presented with a lethal force weapon and our people responded appropriately," he told reporters in Kalgoorlie on Saturday.
"They gave numerous warnings.
"They tried to engage the man, but that wasn't working."
Police later confirmed the man died after two police firearms were discharged during the incident.
"One police officer discharged their firearm twice, and a second police officer discharged their firearm once," WA Police said in a statement.
The shots were fired "after giving the man several warnings, and after the man advanced on them", police said.
Mr Gaunt said cameras worn by the three arriving officers showed the man armed with a handgun and squatting some distance down the laneway.
"From the body-worn video I've seen, the officers acted with great courage, extremely professionally and in accordance with their training," he said.
"I've great admiration for the job they did and the courage they showed in this instance."
WA Police later said the body-worn camera vision had been reviewed and "based on that preliminary assessment it appears the officers involved acted in accordance with policy and their training".
Detectives from the Major Crime Squad and Internal Affairs division arrived in Kalgoorlie from Perth on Friday to investigate.
The man's firearm has since been seized for forensic examination.
"At this time it is not known if it is a working firearm," police said.
The officers involved have been placed on mandatory critical incident leave and have been provided with support from health and welfare personnel.
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