An Australian woman who called 911 to report an assault was shot dead by a Minneapolis police officer after his partner was startled by a loud sound near their car.
The shooting of Justine Damond, 40, on Saturday night, has shocked her family and friends, and was called a "shocking killing" by Australian Prime Minister Malcolm Turnbull.
The Minnesota Bureau of Criminal Apprehension (BCA) said Ms Damond approached the driver's side window of the squad car immediately after the driver had been startled by the sound.
The officer in the passenger seat, Mohamed Noor, fired his weapon, hitting her through the open driver's side window, the BCA said.
The BCA said its information was based on an interview with the officer driving the car, Officer Matthew Harrity, on Tuesday.
Mr Noor declined to be interviewed and the BCA said his lawyer did not indicate when, or if, he would talk to investigators. Under the law he cannot be compelled to talk.
The two officers are on paid administrative leave. Mr Harrity has been with the Minneapolis police department for one year, and Mr Noor for nearly two.
According to the BCA, Mr Harrity told investigators that he and Mr Noor responded to a 911 call from Ms Damond about a possible assault near her home at about 11.30pm on Saturday.
Mr Harrity was driving the squad car as the officers went through an alley to look for a suspect. The squad lights were off.
He told agents he was startled by a loud sound near the cruiser, and immediately afterwards, Ms Damond approached the driver's side window. Mr Harrity said that Mr Noor fired his weapon through the open driver's side window.
No weapon was found at the scene. The officers did not turn on their body cameras until after the shooting, and the squad car camera was also not activated.
Mr Harrity said after the shooting, the officers got out of the squad and gave Ms Damond immediate medical attention.
David Klinger, a criminal justice professor at the University of Missouri-St Louis, said police officers cannot be compelled to testify in an outside investigation.
"Police officers are citizens ... they have the same Fifth Amendment right as anyone. They don't have to give a statement," he said.
"His lawyer might be saying, you're not going to talk until I feel you're rested and not under stress."
The BCA said forensic testing is being completed and evidence is still being examined. When the investigation is completed, it will present all its findings to prosecutors for possible charges.
Mr Turnbull has joined the chorus demanding answers about what happened saying something "clearly went tragically wrong".
He said: "How can a woman out in the street in her pyjamas seeking assistance from police be shot like that? It is a shocking killing.
''We are demanding answers on behalf of her family. And our hearts go out to her family and all of her friends and loved ones. It's a truly tragic, tragic killing there in Minneapolis."
Ms Damond, who was planning to be married next month, was a meditation teacher and life coach.
Her maiden name was Justine Ruszczyk, and though she was not yet married, she had already been using her fiance's last name.