The province's Special Investigations Unit is looking into the sudden death of a 43-year-old man.
Around 1:35 a.m., Wednesday morning, Grey County OPP responded to a residence on Main Street West in Markdale to help Grey County Emergency Services with a call.
While en route to hospital, the victim went into medical distress.
The man was pronounced dead at the hospital.
The SIU has invoked its mandate.
It does so whenever anyone dies or is seriously injured when police officers are involved.
