A man shot dead by police is one of two killed by gunfire in Queensland after a three-hour shooting spree across the state.
Before 11pm on Saturday, three people were injured in a targeted shooting attack in Brisbane city.
The alleged offenders fled the scene and travelled to Brisbane's southwest where they set fire to the vehicle they were travelling in just after midnight.
Two young men, 19 and 20, were arrested and charged with four counts of attempted murder, and a string of other weapons and driving offences.
One suspect is still on the run and police are urging the public for information.
Less than an hour later, a 29-year-old woman was shot at a home north of Brisbane.
Emergency services attended a property on Grant Road in Morayfield just after midnight and tried to help the woman but she died at the scene.
An 18-year-old man was arrested at the same address and police have established a crime scene at the property as investigations continue.
Detective Inspector David Harbison said it was believed the pair knew each other.
"(We) have not yet determined if any relationship exists between the victim and the male, though it's not considered at this stage to be a domestic violence-related incident," he told reporters on Sunday.
Police are trying to figure out why they were at the home together and are still searching for the weapon.
"The victim certainly didn't live at that address and our investigations are just trying to uncover why these persons were at this address," Det Insp Harbison said.
Soon after, police shot dead a 26-year-old man after he allegedly threatened them with a knife at Mount Louisa in Townsville.
Acting Chief Inspector Chris Lawson said the man was believed to be having a mental health episode and was known to police but with "minimal interactions".
He allegedly approached them with a knife, was unsuccessfully tasered and then shot dead.
"The circumstances around exactly what happened with the Taser aren't actually known at the moment," Insp Lawson told reporters.
"Once we've conducted the investigation (and) identified through the body-worn footage what exactly happened, we'll be able to provide that information through to the coroner."
The Ethical Standards Command is investigating on behalf of the coroner, overseen by the Crime and Corruption Commission.