On Monday, Rick Maddison fatally shot Senior Constable Brett Forte after the police officer intercepted his car in Queensland.
He fled to a nearby farmhouse and spent the night in a stand-off with police.
Maddison was killed by authorities after fleeing the house and firing on police, Queensland Police Assistant Commissioner Tony Wright said.
"He has been challenged by police at that point in time - he has fired at those police," he told reporters on Tuesday.
"Specialist police have returned fire. The male person has been shot and that male person has been declared deceased at the scene."
Mr Forte was killed after intercepting Maddison, who police had described as a "wanted person", about 14:20 local time (04:20 GMT) on Monday.
Authorities had set up an exclusion zone around the farm and began negotiating with Maddison at midnight.
The confrontation happened just after 11:00.
On Monday, Queensland Police Commissioner Ian Stewart said he wanted to resolve the siege "as peacefully as humanly possible".
Residents nearby residents were ordered to evacuate their homes on Monday evening.
Mr Forte was a husband and father who had been a police officer for more than 15 years, authorities said.
"It is so distressing - not just to the police service - but to the community, that we have lost a fine police officer," Mr Stewart said.
Queensland Police Union president Ian Leavers said the officer was shot "simply trying to apprehend a wanted person".
"It could have been any one of us anywhere in Australia," he told the Seven Network.
"Our thoughts are with his wife and his three children. He has got a daughter and two sons."
A man who killed a policeman before holding authorities at bay for 18 hours has been shot dead in Australia.