Justine Damond, 40, from Sydney was shot by police in south Minneapolis on Saturday night.
Minneapolis mayor Betsy Hodges said the incident has made her “heartsick”.
Ms Damond died following an officer-involved shooting, according to Minneapolis police.
The shooting occurred on the 5100 block of Washburn Avenue South in the city’s Fulton neighbourhood.
The incident is the subject of an investigation but authorities have said the officers who responded to the 911 call did not have their body cameras turned on.
Two officers responded to a 911 call about a possible assault in the alley off of West 51st Street between Washburn and Xerxes avenues around 11.30pm, according to a statement released Sunday by the Minnesota Bureau of Criminal Apprehension.
“At one point one officer fired their weapon, fatally striking a woman,” the BCA said.
The dead woman’s partner was Don Damond.
His son Zach Damond took to Facebook saying he “heard noise in the alley and called the police”.
“She was out on 51st Street and she was shot,” Zach said.
“Investigators are attempting to determine whether any video of the incident exists.”
Mr Damond said the woman, reportedly an Australian in her 40s, was “passionate” and his “best friend”.
“Basically my mum was shot for reasons I don’t know,” Mr Damond said in a video posted on Facebook on Monday morning (AEST).
“I just know she heard a sound in the alley so then she called the police and the cops showed up and she was a very passionate woman…