Justine Damond, formerly of Sydney, was shot and killed near her Minneapolis home on Saturday night.

A timeline pieced together through the bride-to-be’s 911 calls and a newly released police incident report shows Ms Damond was shot two minutes after police officers arrived at the alleyway behind her home.

What it doesn’t explain is what happened in those two crucial minutes that prompted officer Mohamed Noor to draw his gun, reach over his partner and discharge his weapon through the open window, delivering a fatal shot to Ms Damond’s abdomen.

The incident report shows officers arrived 12 minutes after the concerned resident’s initial 911 call at 11.39pm when she reported a suspected sexual assault.

At this time, officers indicated the situation was under control and no back up was required.

Two minutes later, the caller was dead. Officers reported shots had been fired, they had “one down”, and emergency back up was needed.

Justine Damond was fatally shot by police in Minneapolis on Saturday. Picture: Stephen Govel/www.stephengovel.com via APSource:AP

A timeline of the calls and police response shows what we know.

11.27pm: First 911 call. Ms Damond reports she hears a woman “having sex or being raped” in the alley behind her home on 51st St and Washburn Ave. The operator says they have “already got an officer on the way.”

“What is your name?” the officer asks.

“JUSTINE.”

11.35pm: Second 911 call. Ms Damond calls emergency services again saying no one has arrived and checks if officers got the address wrong. “Are you JUSTINE?” the operator asks. “You’re hearing a female screaming?”

Ms Damond confirms and is told “officers are on the way there”.

11.39pm: Police arrive. A squad car, driven by officer Matthew Harrity with officer Mohamed Noor in the passenger seat, arrive at the address. The officers report on police radio the incident is a “Code four”, meaning no back up is required.

11.41pm: Shooting reported. The situation has completely changed. Officers call for back up requesting a police, fire and emergency response. The incident report notes at this time: “ONE DOWN... STARTING CPR.”

Police radio transcript from the time shows officers reported: “Shots fired at Washburn and 53rd Street. Correction 51st. Sergeant to acknowledge shots fired and one down at Washburn.”

11.46pm: Police radio in to confirm there are “no suspects at large”.

11.49pm: Incident report shows police “have been doing CPR for last four minutes”. “Two additional police units have arrived on the scene.”

Minneapolis police officer Matthew Harrity, who was on patrol with Mohamed Noor when he shot Australian woman Justine Damond.Source:Supplied

Minneapolis police officer Mohamed Noor, who fatally shot Justine Damond. Picture: City of Minneapolis via APSource:AP

A new account published by a local news outlet suggest a pounding on the police car led Mr Noor to believe he was being ambushed when he shot and killed Ms Damond.

The independent investigation into Saturday night’s fatal shooting has revealed that the officers were “startled by a loud sound” before Mr Noor shot Ms Damond.

Citing an anonymous source, the Minneapolis TV station KSTP reported that the officers were sent to the alley off Ms Damond’s home after she reported that a possible assault was under way.

When they failed to notice anything suspicious when patrolling the area in the police car, they were dispatched to another incident.

Before departing the scene, they saw a young man ride past on a bicycle.

As the officers watched the cyclist ride past on the passenger side of the vehicle, they were startled by a pounding on the driver’s side, the source said.

The sound led the officers to believe they were “caught in an ambush”, KSTP reported, and Mr Noor fired his gun, which was in his lap at the time.

The bullet fired past Mr Harrity in the driver’s seat, through the open driver’s side window and struck Ms Damond in the abdomen.

The officers performed CPR on the 40-year-old until paramedics arrived but she died at the scene.

The KSTP report matches with an account of the shooting given by a friend of Mr Noor, who said Ms Damond “startled” him before he opened fire.

The friend told the Daily Mail that he and his colleague saw a panicked figure in the dark who rushed towards their vehicle, which was patrolling the area with its lights off. The figure, who they perceived to be a threat, turned out to be an unarmed Ms Damond holding a mobile phone.

“Mohamed believes he acted to protect himself and his colleague, but accepts since that she was not armed,” the unnamed friend said.

“It was over in seconds and it was a very tense moment. He is sorry for the woman and her family.

“But he would never have opened fire without genuinely feeling in danger.”

The friend also told the Mail that he felt he had been “thrown under the bus” by his police colleagues.

“His colleagues are accusing him of not showing proper police conduct on Saturday night,” the friend said.

On Wednesday, Mr Harrity’s lawyer, Fred Bruno, backed the theory that the officers believed they were being ambushed.

“It’s certainly reasonable to assume that any police officer would be concerned about a possible ambush under these circumstances,” Mr Bruno told Minneapolis’s Star Tribune newspaper.

“It was only a few weeks ago when a female NYPD cop and mother of twins was executed in her car in a very similar scenario.”

Mr Bruno was referring to the case of police officer Miosotis Familia, who was patrolling New York’s crime-ridden Bronx borough on July 5 in a police car when a mentally ill man walked up and shot her in the head through the passenger window.

Meanwhile, the anonymous source told KSTP that the mystery cyclist who was on the scene filmed the aftermath of the shooting — which would be a crucial piece of evidence if it exists.

However, the Bureau of Criminal Apprehension, which is investigating the killing, maintains that its investigators are not aware of any video or audio of the incident.

The bureau has asked for the cyclist, described as an 18- to 25-year-old caucasian, to come forward and tell investigators what he saw.

Justine Damond’s fiance Don Damond hugs a neighbour after speaking to the media in Minneapolis.Source:Supplied

The KSTP report goes against the theory that the sound the officers heard on Saturday night was fireworks. This idea gained traction after an officer said during the police radio conversation after the shooting that “aerial fireworks” may have been let off in the area.

Mr Noor has refused to be interviewed by investigators and the BCA has no legal power to force him to give evidence.

“We cannot compel officer Noor to make a statement,” Minneapolis mayor Betsy Hodges told reporters on Tuesday. “I wish we could.”

Minneapolis mayor Betsy Hodges and assistant police chief Medaria Arradondo discuss the latest developments in the death of Justine Damond. Picture: Richard Tsong-Taatarii/Star Tribune via APSource:AP

Mr Noor’s family broke their silence on the case on Wednesday, implying the shooting was a tragic mistake.

“We feel so bad about this, we are traumatised ourselves. It’s so unfortunate,” a family member said.

“If you wait for the investigation you’ll know it was an honest and sincere event that transpired. Until then we can’t really say anything.”

Mr Harrity was “stunned” when his colleague opened fire on Ms Damond, a source told local TV station KARE 11 on Tuesday.

Both officers are now on paid leave.