Justine Damond: 911 call transcripts reveal series of events that led to fatal shooting of Australian woman

Justine Damond was killed by a police officer responding to her report of a suspected rape outside her home in Minneapolis

Police have released transcripts of 911 calls that led to an Australian woman being shot dead after reporting a suspected rape near her home in the US.

Justine Damond made two emergency calls in which said she could hear a "distressed" woman calling for help in an alley behind her house in Minneapolis.

The 40-year-old meditation coach was shot and killed minutes later by an officer responding to her report.

In her first call, made at 11.27pm on 15 July, she tells the control room: "I can hear someone out the back and I’m not sure if she’s having sex or being raped.

"I think she just yelled out 'help', but it’s difficult. The sound has been going on for a while, but I think, I don’t think she’s enjoying it."

She adds: "It sounds like sex noises, but it’s been going on for a while and I think she tried to say help and it sounds distressed."

The call ends after the operator tells Ms Damond an officer has been dispatched.

Eight minutes later she calls back to say police had not yet arrived, and "wondering if they got the wrong address". The operator assures her officers are on their way.

Justine Damond was known as Justine Ruszczyk before she took on the last name of her husband, who she had plans to marry next month (Courtesy Stephen Govel/Stephen Govel Photography/Handout via REUTERS) (Reuters)

Moments later Ms Damond was shot dead in her pyjamas by officer Mohamed Noor as she approached the driver's side window of his police car.

There are no known witnesses to her killing other than Mr Noor and officer Matthew Harrity, who was behind the wheel. Mr Noor has so far refused to give his account of events.

The officers did not turn on their body cameras until after the shooting, and the police car's camera was also not activated.

In police radio recordings, the officers can be heard calling for backup and attempting to perform CPR on Ms Damond, who had been due to marry next month.

"Shots fired... we got one down," one of the officers can be heard to say.

Mr Harrity said the pair had been startled by a "loud sound" seconds before Ms Damond approached their car and Mr Noor shot her in the abdomen.

Minneapolis Police has opened a use-of-force investigation, as is standard each time an officer discharges a weapon.

The police department's internal affairs unit can compel Mr Noor to give a statement as part of its own investigation and fire him if he refuses.

But that statement cannot be used against him in any criminal investigation, to which the officer has the right to remain silent.

Mohamed Noor fatally shot Justine Damond (City of Minneapolis via AP)

Details emerged on Wednesday that raised questions about whether proper police procedures were followed before Ms Damond's shooting.

Local TV station KSTP, citing a source it did not name, reported the two officers thought they were being targeted in an ambush when they heard a pounding noise on the driver's side. Mr Noor had his gun on his lap.

Mr Harrity's attorney, Fred Bruno, told the Star Tribune it was "certainly reasonable" for the officers to fear a possible ambush.

Several criminal law professors told Associated Press it would be unusual if the officer had his gun out when officers were checking out a report of a potential assault. But he might have already been in a heightened state of awareness in light of recent ambushes of police, they added.

Officers searched the area and found no suspects or signs of the suspected rape.

Sydney-born Ms Damond, known as Ms Ruszczyk before she took her fiancé's name, moved from Australia to Minneapolis to be with her partner Don Damond and his 22-year-old son Zach.

Australian Prime Minister Malcolm Turnbull has joined her family in demanding answers over the "shocking killing".