The US police officer who shot dead Australian woman Justine Damond may have been startled by nearby fireworks, it has emerged, as the city’s mayor urged the shooter to come forward and tell his story.

In the first official account of events of when Ms Damond was killed on Saturday night, Minnesota’s Bureau of Criminal Apprehension (BCA) on Wednesday [AEST] confirmed that Officer Mohamed Noor who fired the fatal shot, had refused to be interviewed.

But his on-duty partner Matthew Harrity has spoken to investigators, telling the BCA that he had had been “startled by a loud sound near the squad” car as he drove the vehicle down an alley behind Ms Damond’s home.

In police radio conversations between the two officers, the police dispatcher and other responders, the dispatcher refers to “two shots heard from the east”.

“We heard those sounds from the station,” an officer responds. “Those are probably aerial fireworks.”

Officer Harrity said Ms Damond had approached the driver’s side window of the car immediately after the sounds, when Officer Noor fired his gun through the open driver’s side window, striking Ms Damond. 

Ms Damond, 40, died at the scene from a gun shot to her stomach, after the two officers tried for 20 minutes to keep her alive.

Ms Damond, who was raised in Sydney, died in her pyjamas on Saturday night after calling Minneapolis police for help, after hearing screams and fearing an assault was occurring in an alley behind her home.

Come forward, mayor tells police officer

Meanwhile, Minneapolis Mayor Betsy Hodges has voiced her frustration at not being able to force Officer Noor to be interviewed by investigators, and urged the police officer to give his version of events.

“We do have more information, though it’s frustrating to have some of the picture but not all of it,” Ms Hodges told a press conference on Wednesday [AEST].

“We cannot compel Officer Noor to make a statement. I wish we could.

“I wish that he would make a statement,” she said.

Mayor Betsy Hodges and assistant police chief Medaria Arradondo address the media. Photo: AAP

Questions still remain over why neither officer’s body camera nor the squad car dash camera were on at the time of the incident.

Assistant police chief Medaria Arradondo confirmed that officers Noor, 31, and Harrity, 25, had only 21 months and one year’s experience respectively.

When quizzed about the officers’ relative inexperience Asked by the media about partnering two relatively inexperienced officers, Mr Arradondo said: “These were two fully trained police officers.”

He added that the Minneapolis police had a “quality assurance commander” who would complete a full investigation, while a simultaneous “use of force” investigation had also been been launched.

Officer Noor has declined to be interviewed by BCA agents, and his lawyer has not provided clarification on when, if ever, an interview would be possible.

“We cannot compel Officer Noor to make a statement … but I wish that he would,” Mayor Hodges said.

Police want to talk to mystery witness

A mystery man on a bicycle could provide key answers to questions surrounding Ms Damond’s death, the BCA update said.

Officer Harrity told the investigation the pair had seen a white male aged between 18 and 25 years old on a bicycle immediately before the shooting.

The man reportedly stopped at the scene and watched as the officers provided medical assistance to Ms Damond after Officer Noor had shot her, the BCA said.

– with AAP