Relatives of an Australian woman shot dead by US police have said she made an emergency call to report a sexual assault before the incident.

They demanded answers about the mysterious shooting in which the meditation teacher was reportedly killed by an officer who fired from the passenger seat of a squad car as the victim stood outside the driver’s door.

The authorities in Minneapolis released no details about what led to the shooting of Justine Damond, whose fiance said she had called 911 to report what she believed was a sexual assault in an alley near her home.

A makeshift memorial is left at the scene where a Minneapolis police officer shot and killed Justine Damond(Elizabeth Flores/AP/PA)

Police said officers were responding to a call about a possible assault late on Saturday when she was killed. There were no known witnesses other than the two officers in the squad car.

A newspaper report said Ms Damond was shot while standing alongside the car in her pajamas.

Her fiance, Don Damond, said the family has been given almost no additional information about what happened after police arrived.

“We’ve lost the dearest of people, and we’re desperate for information,” he said. “Piecing together Justine’s last moments before the homicide would be a small comfort as we grieve this tragedy.”

Don Damond is comforted by friends and familyDon Damond is comforted by friends and family (Elizabeth Flores/Star Tribune via AP)

Ms Damond’s family members in Australia said they “are trying to come to terms with this tragedy and to understand why this has happened”.

Authorities did not release the woman’s name, but the Star Tribune identified her as Ms Damond, from Sydney, Australia. The newspaper reported that she was engaged to be married in August and was using her fiance’s last name. Her maiden name was Justine Ruszczyk.

Almost two days after her death, police offered no public explanation and referred questions to the state’s Bureau of Criminal Apprehension, which was investigating.

The BCA said on Monday that no weapons were found at the scene.

Don Damond is comforted by his son ZachDon Damond is comforted by his son Zach (Elizabeth Flores/Star Tribune via AP)

Local media identified the officer who fired as Mohamed Noor, who is a Somali-American and joined the police department in March 2015.

His lawyer, Tom Plunkett, released a statement saying Mr Noor offered his condolences to the family “and keeps them in his daily thoughts and prayers”.

The statement added: “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 empathises with the loss others are experiencing.”

Justine DamondJustine Damond (Stephen Govel/www.stephengovel.com via AP)

The Star Tribune, citing three people with knowledge of the shooting it did not name, said the officers pulled into the alley in a squad car, and Ms Damond talked to the driver.

The newspaper’s sources said the officer in the passenger seat shot Ms Damond through the driver’s-side door.

Neighbour Joan Hargrave called the killing “an execution” and said there was no reason for a well-trained officer to see Ms Damond as a threat.

“This is a tragedy — that someone who’s asking for help would call the police and get shot by the police,” Ms Hargrave said.