Minnesota cops are desperately searching for a mystery bicyclist who was seen moments before a Minneapolis police officer shot and killed an unarmed woman Saturday night and who may be the lone independent witness to the controversial killing.

The bicyclist, estimated to be between 18 and 25 years old, was seen in the area shortly before the fatal shot was fired and allegedly stuck around to watch officers Mohamed Noor and Matthew Harrity try in vain to resuscitate Justine Damond, investigators said Tuesday night.

As the search for answers continues into how Damond, who called police after hearing screams nearby, was killed, the bicyclist may be an essential witness. Noor, who reportedly shot Damond, isn’t talking to investigators.

Harrity was interviewed by the Minnesota Bureau of Criminal Apprehension and provided a detailed rundown of the night, including that both officers heard a loud noise near their squad car shortly before Damond, a native Australian, approached the driver’s side of the police cruiser. In the ensuing moments, and for an as-yet unidentified reason, Noor, seated on the passenger’s side, fired his weapon through the open driver’s side window, striking Damond.

Neither officer activated his body camera during the incident – an apparent violation of department policy. The squad car’s dash camera also wasn’t recording.

In the absence of definitive footage, BCA agents have asked the bicyclist seen in the area – and anyone else who may have seen the shooting – to come forward.