The state agency investigating the fatal police shooting of an Australian woman in Minneapolis last weekend said on Tuesday that one of the officers in a police car had been startled by a noise outside the car moments before his partner shot the woman through the open driver’s-side window.

The statement from the agency, which came three days after the shooting, gave a glimpse into an episode that has baffled the public and infuriated the family of the woman, Justine Damond, in both Australia and Minneapolis.

But it did not include information from Mohamed Noor, the 31-year-old officer who fired the shot that killed Ms. Damond. Officer Noor declined to be interviewed by investigators. “Officer Noor’s attorney did not provide clarification on when, if ever, an interview would be possible,” the statement said.

Investigators interviewed Officer Matthew Harrity, who has been with the Minneapolis Police Department for a year and was behind the wheel when the shooting happened.