A woman was leaving for a sporting activity when a neighbour allegedly shot her dead in her car in front of two girls.
Ryan Geoffrey Cole, 31, has been accused of killing the woman and shooting a good Samaritan in Mackay, north Queensland, after the girls raised the alarm.
Police hailed the bravery of the girls, aged 11 and 12, after Cole was charged with murder on Thursday.
Police are investigating how Cole allegedly gained access to a firearm after having a weapons licence revoked three years ago.
Cole was a neighbour but did not know the 34-year-old woman who was parked in her driveway ready to leave with the children on Wednesday afternoon, police said.
"They were heading out to some sort of sporting activity," Detective Acting Superintendent Emma Novosel told reporters.
Cole allegedly approached the woman as she sat in the vehicle with the girls before shooting her.
"It's obviously a tragic incident where two young girls have witnessed a violent death," Supt Novosel said.
"I want to acknowledge and commend their bravery for actually managing to remove themselves from such a dangerous situation and raise the alarm.
"It's incredibly brave and I can't even begin to imagine the trauma that they must be experiencing."
The woman died at the scene.
The girls fled the car unharmed and alerted a 66-year-old male neighbour.
He came to the woman's aid but was allegedly shot by Cole, suffering hand and chest injuries.
The good Samaritan remains in the Mackay Base Hospital in a serious but stable condition.
Cole had what witnesses described as a revolver-type weapon, police said.
He is accused of driving away, sparking an emergency lockdown of the area and a police manhunt.
Cole was arrested outside a nearby service station hours later.
"Certainly at this stage, the motives behind the attack on this woman and man are unknown so there'll be further investigations to determine what’s bought about this incident," Supt Novosel said.
The accused had "very minimal" interactions with police in the past and officers had not previously been called to his street for help, she said.
Police Commissioner Steve Gollschewski described the Mackay incident as a "horrid situation".
"A life has been lost ... (in) a really terrible act of violence by the offender and another person has been seriously injured," he said.
Mr Gollschewski said the accused previously had a weapons licence but it was revoked in 2021, with 11 firearms taken from him.
"That was as a result of his conduct and other charges that he'd faced that the weapons were removed from him and the licence was revoked," he said.
"We'll look really closely not only at what occurred yesterday, but the lead-up to that in terms of his access to weapons and how he might have got that weapon."
Mr Gollschewski said additional powers were being sought via a firearms prohibition scheme before state parliament to thwart similar incidents.
Cole was charged with murder and attempted murder, appearing via videolink in Mackay Magistrates Court on Thursday.
He was remanded in custody.
