Queensland police who shot a man in a four-wheel-drive on Tuesday believed nobody was inside the vehicle until it suddenly accelerated towards them.
A 29-year-old was shot in the head and arm by the two officers at a property on Priestdale Road in Rochedale South, about 20 kilometres south of Brisbane.
He remains in the Princess Alexandra Hospital intensive care unit in a critical condition.
The two male senior constables were responding to reports of a stolen ride-on mower, which had been tracked to the large property.
Witnesses said they heard four or five shots about 8.30am.
Neither officer suffered serious injuries, although it is believed one of the officers was clipped by the four-wheel-drive.
A second man who was in the vehicle was not injured and was taken into custody.
Police will now conduct an ethical standards investigation, as is standard practice when an officer's weapon is discharged.
Queensland Police Union president Ian Leavers said both officers would be offered counselling and assistance.
"When police got out of their car, near the trailer, they believed [the four wheel drive] was unoccupied," Mr Leavers said.
"Suddenly it started driving at the two officers who have immediately been in fear of their lives. They've drawn their service firearms and fired some shots towards the driver.
"This shows the difficult and dangerous nature of police work. They were attending to a routine investigation and suddenly became in fear of their lives and did what they needed to do to protect themselves."
Mr Leavers said the driver was known to police.
Fairfax Media believes the allegedly stolen lawn mower belongs to a nearby landscaping company. One of its vehicles was parked out the front of the property on Tuesday morning, however staff at the company's Logan office referred all inquiries to police.
Acting Inspector Stephen Hollands said police were responding to reports of a stolen ride-on mower, which was found in a trailer attached to the four-wheel-drive.
"At this point in time the investigation is at a very early stage," Acting Inspector Hollands said.
"It's certainly concerning that the police were in a situation where they had to resort to that use of force."
