Pictured: US cop 'who shot dead Australian woman in her pyjamas'

The policeman who shot dead an Australian woman after she called 911 to report an alleyway assault near her Minneapolis home has been identified as a junior officer with two years' experience.

Officer Mohamed Noor was reportedly sitting in the passenger seat of a police car when he leaned over and allegedly shot across his partner, killing former Sydney resident Justine Ruszczyk Damond about 11.30pm Saturday local time local media reports.

Officer Matthew Harrity was driving the car, however neither had their body cameras switched on when the shooting occurred.

The 40-year-old was in her pyjamas when she began speaking to Officer Harrity but what came next will be the subject of major investigation.

Local media has reported a phone was found next to Ms Ruszczyk Damond's body, raising the prospect police thought she was carrying a gun.

Officer Mohamed Noor was allegedly sitting in the passenger seat of a police car when leaned over and shot across his partner. Source: Minneapolis Police Department

Justine Ruszczyk Damond was shot dead by police outside her Minneapolis home. Source: AAP

Twenty-four hours after her death, police confirmed Ms Ruszczyk Damond was unarmed.

The Minnesota Bureau of Criminal Apprehension, which investigates all officer-involved shootings in the state, would not say what precipitated the shooting.

Noor, who was the first Somali-American police officer in his precinct, was previously praised by Minneapolis Mayor Betsy Hodges.

Noor issued a statement through attorney Tom Plunkett Monday afternoon:

"Officer Noor extends his condolences to the family and anyone else who has been touched by this event. He takes their loss seriously and keeps them in his daily thoughts and prayers," the statement read.

"He came to the United States at a young age and is thankful to have had so many opportunities. He takes these events very seriously because, for him, being a police officer is a calling. He joined the police force to serve the community and to protect the people he serves. Officer Noor is a caring person with a family he loves and he empathizes with the loss others are experiencing.

"The current environment for police is difficult, but Officer Noor accepts this as part of his calling. We would like to say more, and will in the future. At this time, however, there are several investigations ongoing and Officer Noor wants to respect the privacy to the family and asks the same in return during this difficult period."

Mohamed Noor joined the department in March 2015. Source: Facebook

After the fatal shooting, Mayor Hodges' tone changed considerably.

"I am heartsick and deeply disturbed," she told reporters.

"We have few facts at this point, we all want to know more."

Hodges was particularly interested in finding out why the officers' body cameras were not turned on during the fatal encounter. All Minneapolis police are outfitted with the cameras.

Ms Ruszczyk Damond was engaged to marry her 50-year-old partner Don Damond in August.

Don Damond said he had been left in the dark as to why authorities shot and killed the woman he was supposed to marry. Source: Twitter

Now the man she was supposed to marry next month said he has been completely left in the dark by authorities.

"Our hearts are broken," Don Damond said in an emotional press conference.

"As you know, it was her who called 911 on Saturday evening, reporting what she believed was an act of sexual assault occurring nearby.

She had become a step-mother to his 22-year-old son, who posted a heartbreaking video in the morning after her death.

“Basically my mum's dead because a police officer shot her for reasons I don't know,” he said.

Zach Damond said he's "demanding answers" as to why police shot dead his step-mother. Source: Facebook

“I demand answers. If anybody can help, just call police and demand answers. I'm so done with all this violence, America sucks.

“She was a very passionate woman, she thought something bad was happening.

"Next thing you know they take my best friend's life.”

Minneapolis Police Chief Jane Harteau released a statement saying: "I want to acknowledge the pain and frustration that family and community members have following a fatal officer involved shooting".

"This is clearly a tragic death," Chief Harteau wrote.

"I also want to assure you that I understand why so many people have so many questions at this point.

"I have many of the same questions and it is why we immediately asked for an external and independent investigation into the officer-involved shooting death.

"I've asked for the investigation to be expedited to provide transparency and to answer as many questions as quickly as we can."