Yellow police tape draped an area near Nelson Square, a park on Kempenfelt Drive, in Barrie on Saturday afternoon.
Barrie police spokesman Peter Leon told Barrie 360 that they were unable to comment and the province's Special Investigation Unit (SIU) had invoked its mandate.
Numerous first responders were in the area, including police tactical officers.
The SIU has not commented.
The civilian agency is required to investigate situations involving police and civilians that result in serious injury, sexual assault or death.
Images supplied - MICHAEL CHORNEY