From the NPR article linked above:
As MPR's Doualy Xaykaothao has reported, the Australian yoga and meditation instructor — who went by the name Justine Damond in her professional life — was shot and killed by Minneapolis Police Officer Mohamed Noor. He and a fellow officer had been responding to a 911 call Saturday night.
Tuesday evening, a state agency investigating the shooting said the other officer on the scene, Matthew Harrity, told investigators that when they arrived, he was startled by a loud sound near the patrol car. He said immediately after the noise Justine Ruszczyk approached Harrity's side — the driver's side — of the car. Harrity said at that point, Noor fired his gun through the open driver's window, striking the woman.
Sounds like a very jumpy cop who drew and fired while still seated in his cruiser.