South Australia's Police Commissioner Grant Stevens has described the overnight shooting and backed the four officers involved for acting appropriately.
Police were called to reports of a mental health incident involving a man hurting himself with the weapon at Craigburn Farm in Adelaide's south just after midnight on Tuesday.
Mr Stevens said the 40-year-old confronted police with a knife and when officers unsuccessfully deployed their Tasers he continued to charge at them, so they opened fire.
Paramedics treated the man on the way to hospital where he later died.
Police chief Grant Stevens says officers were faced with a "highly stressful, dangerous situation". (Naomi Jellicoe/AAP PHOTOS)
"I can say that having watched the body-worn video that this was a highly stressful, dangerous situation," Mr Stevens told reporters on Tuesday.
"The police officers appear at this time to have acted in accordance with their training and taken the action necessary to protect themselves and the ambulance officers who were on the scene."
More than one of the police involved fired shots but the exact number of bullets involved is not yet known.
The police chief said he didn't know why the Taser had failed however the man was covered in a blanket which may have prevented the taser's barbs acting as intended.
The man was alone at the time and his girlfriend raised the alarm after a video call where it became apparent he had harmed himself and was threatening to continue doing so, Mr Stevens said.
No officers were injured during the incident.
Detectives from the major crimes squad, specialists from the forensic response section and the force's internal investigation team are investigating what happened.
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