Authorities were called to Tamar Street in the Brisbane suburb of Annerley on Friday about 9.13am after reports of a man in the backyard of a home he did not live at, wielding a piece of wood.
A 40-year-old constable and junior constable approached the man in attempts to de-escalate his "agitated" state, before the 26-year-old male allegedly lunged at the senior officer.
"The male approached the officers and a struggle commenced, and ... the offender lunged for a firearm belonging to the senior constable," Acting Assistant Commissioner Rhys Wildman told reporters.
"During the struggle for that particular firearm, the firearm discharged and the senior constable received a gunshot wound to the left inner thigh."
The junior constable then shot the 26-year-old twice in the stomach before providing first-aid to his fellow officer via a tourniquet.
More officers arrived shortly after and needed to deploy a Taser on the 26-year-old who remained agitated after his two gunshot wounds, Mr Wildman added.
The junior constable was also bitten by the offender during the altercation.
"This is how dynamic the situation was," Mr Wildman said.
It was "extremely" unusual to deploy a Taser after a suspect has been shot, reporters were told. (Darren England/AAP PHOTOS)
"He's tending to his partner and also this male is still agitated, and hence the second crew attended and have to deploy a Taser.
"This is a very, very unusual set of circumstances with a very committed male."
Mr Wildman said it was "extremely" unusual to deploy a Taser after a suspect has been shot.
"The briefing provided just reinforces the dynamic nature of this incident and extremely difficult circumstances that those two officers faced in responding to what on face value, appeared a fairly simple call."
The suspect and two officers were taken to the nearby Princess Alexandra Hospital where the 26-year-old offender is undergoing surgery in a serious condition, and the 40-year-old senior constable remains stable.
The junior officer was treated for a bite wound and has since been released.
Premier David Crisafulli said an incident such as this "sends a shiver up your spine". (Darren England/AAP PHOTOS)
"Policing is an extremely dangerous profession," Mr Wildman said.
"It involves officers attending jobs such as this, where a simple job can very quickly escalate into something that becomes a life-threatening situation. So our thoughts go out to the officers concerned."
Earlier on Friday, Premier David Crisafulli said an incident such as this "sends a shiver up your spine".
"It shows you why people respect the men and women in the Queensland Police Service so very much," he told reporters.
"They run towards situations where others naturally run away and there's no place for that in modern Queensland."
An investigation into the incident will be undertaken by the Ethical Standards Command with oversight by the Crime and Corruption Commission.
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