Four officers went to the isolated rural residence earlier on Monday to investigate reports of a missing person believed to be a former NSW school teacher and were met with a hail of bullets.
Police returned fire but the two officers were critically injured and died at the scene. Another two were wounded when at least two gunmen opened fire at the property, at Wains Road in Wieambilla, at 4.45pm.
Authorities say a siege situation ensued and specialist police and PolAir responded.
"Two males and a female were fatally shot during a confrontation with police shortly after 10.30pm," the force said in a statement early Tuesday morning.
AAP has been told the three attackers were killed in a firefight with officers. According to police sources, the men were brothers and the woman, one's partner.
It is understood the officers who died during the earlier ambush - one male, one female - were constables in their 20s who had been stationed at nearby Tara.
Police Commissioner Katarina Carroll said the horrific incident was devastating for the victims' families and the entire organisation.
The commissioner fought back tears as she confirmed the initial deaths of the three people, including her two officers, at the late-night media conference on Monday.
"I would like to also pay tribute to all police and first responders who assisted at the scene and are continuing to respond this evening," she said.
"Tragically, this is the largest loss of life we have suffered in one single incident in recent times ... It is devastating news."
An emergency declaration remained in place on Tuesday morning for the Wieambilla area and a crime scene had been established at the property.
Queensland Police Union president Ian Leavers said "the behaviour of these murderers tonight is absolutely unacceptable".
He described the attack as "a ruthless, calculated and targeted execution of our colleagues and loved ones" and the slain officers as young and "very junior in service".
Prime Minister Anthony Albanese earlier said it was a heartbreaking loss for the families and friends of those who had lost their lives in the line of duty.
"My condolences to all who are grieving tonight - Australia mourns with you," he tweeted.
Opposition leader Peter Dutton, a former Queensland police officer, was also moved by the tragedy.
"Deeply distressing news coming out of western Queensland tonight with those police officers who have been murdered," he wrote.
"Police officers face danger every day to keep us from it."
Premier Annastacia Palaszczuk said the deaths were a "horrible tragedy" as Western Downs regional council mayor Paul McVeigh said his community was shattered.
"It's an absolute tragedy in our community," Cr McVeigh said.
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