Family rang police this afternoon.
Acting Assistant Commissioner Investigations Glenn Dunbier said the man had been taken into custody by police and was lying on the ground when it appeared a police firearm was accidentally fired towards the man.
Police spokeswoman Kris McGehan said the shot man was in a critical condition. She would not say where the man had been shot.
St John ambulance had been told by police not to comment.
Mr Dunbier said two investigations into the shooting were underway by police and the Independent Police Conduct Authority.
Police were speaking with the man's family this evening.
"This is a very serious event that police will be looking into thoroughly,'' Mr Dunbier said.
"We will be interviewing everyone who was at the scene at the time of the incident as part of our investigations. Our thoughts are with the man and his family at this time and we will be liaising closely with them,'' Mr Dunbier said.
