Ms Ruszczyk was unarmed and in her pyjamas when she was shot dead by junior officer Mohamed Noor in July after calling 911 twice to report a suspected sexual assault in a laneway behind her home.

The 40-year-old woman had spent the morning of her death trying on wedding dresses for her marriage in Hawaii in August.

Her family have revealed they are still waiting to hear whether criminal charges will be laid over her death.

Her fiance, Don Damond, who was on the phone to Ms Ruszczyk in the moments before her death, told ABC's Australian Story on Monday night that he still struggled to comprehend how the act of dialling 911 for help could lead to such a tragedy.

The night she died Ms Ruszczyk called Mr Damond after being spooked by noises she believed related to a sexual assault in the laneway.

He told her to hang up and phone police.

"There's a number of things that had to line up for this to happen in the way that it did," Mr Damond said.

"I was away. I was out of town on a business trip, on a Saturday. That night I told Justine to call 911, I had this conception that when she said, 'the police are here,' I felt like all is well, like the knights in shining armour have arrived. I'll never feel that way again."

Minneapolis civil rights lawyer Robert Bennett, who is acting for the family, said a decision about criminal charges was unlikely to be rushed by Hennepin County Attorney Mike Freeman.

He said it was the worst example of excessive force he'd ever seen.

"It's a use of force so beyond the pale that it would cause other people not to call the police," he said.

"That's what outlines this as something unique. There's no excuse for it. If she can be shot, anybody can be shot. Any 911 caller, any mother in her pyjamas, anybody can be shot.

"You can't just say it's an accident. I can't imagine that they teach officers that one of the good lines of fire is across the lap of their driving partner. I mean, it's just crazy.

"In Minnesota we've never convicted an officer for any form of homicide or manslaughter in connection with an officer-involved shooting, or other killing of the suspect.

"I would charge someone in Justine's case."

???Criminal justice advocate Jason Sole said the US had an entrenched problem with police violence.

"In no just society should you be the one calling police for help and end up dead," he said. "We have a longstanding problem and it's time for us to fix it."

He detailed the case of Philando Castille, an African-American man shot and killed during a traffic stop.

There was outcry across the African-American community when the officer responsible escaped conviction.

Since 2000, 162 people have died in encounters with the Minnesota police.

Charges have been laid against only one Minnesota police officer and he was never convicted of the shooting.

Her father, John Ruszczyk, vowed the family would not rest until the truth came out and somebody was held accountable for her death.

"This event has changed my life. It's stolen 40 years of my daughter's life. That's a very big crime as I see it," he said. "She would have wanted us to go to the end, of seeing some change. And her death is not something that can be washed away."

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