A US police officer reportedly shot dead Australian spiritual healer and "beautiful soul" Justine Damond after she approached his squad car in a Minnesota alley and began speaking to his partner through the driver's seat window.
Ms Damond called police in her adopted home city of Minneapolis just before midnight on Saturday about a possible assault in the alley behind her home.
When the police car arrived, the 40-year-old, dressed in her pyjamas, walked to the driver's side door and began talking to the driver, according to the Minneapolis Star-Tribune citing three sources with knowledge of the incident.
The alley was described as well-lit, but according to the sources the officer sitting in the passenger seat pulled his gun and shot Ms Damond through the driver's side door.
No weapon was found at the scene, the two officers' body cameras were not turned on and their police car dashboard camera did not capture the incident.
The two police officers are on administrative leave, while the city's mayor wants to know why the cameras weren't on.
Ms Damond's soon-to-be stepson, Zach Damond, was desperate for answers.
"My mum is dead because a police officer shot her for reasons I don't know," the 22-year-old said.
"I demand answers.
"If anybody can help, just call police and demand answers.
"I'm so done with all this violence."
Her family in Sydney has called for privacy.
"This is a very difficult time for our family. We are trying to come to terms with this tragedy and to understand why this has happened," they said in a statement.
"We will not make any further comment or statement and ask that you respect our privacy."
Minneapolis and its twin city St Paul are still reeling from the acquittal last month of a police officer who shot dead a man, Philando Castile, during a traffic stop while Castile's girlfriend live streamed the horrifying incident.
"I am heart sick and deeply disturbed by the fatal officer involved shooting last night," Minneapolis Mayor Betsy Hodges told reporters.
The mayor said there were a "lot of questions" why the police body cameras were not on.
A placard placed at a vigil near the Australian's home in Minneapolis' Fulton neighbourhood asked: "Why did you shoot and kill our neighbor and friend?"
Ms Damond, originally from Sydney and who also went by the name Justine Ruszczyk, was set to marry US businessman Don Damond next month.
Mr Damond was away on business on Saturday.
Ms Damond, according to her website, was a vet and became a spiritual healer and meditation coach.
She focused her life on helping to "heal and transform" people "after she saw family members suffer greatly from depression, alcoholism and cancer".
Minnesota's Bureau of Criminal Apprehension said the investigation was in its early stages.
"Two Minneapolis police officers responded to a 911 call of a possible assault just north of the 5100 block of Washburn Avenue South just before 11.30pm Saturday," the BCA said in a statement.
"At one point an officer fired their weapon, fatally striking a woman."
© AAP 2017