Police on Vancouver Island are trying to determine why an RCMP officer shot a 40-year-old man during a traffic stop in Chemainus.

In a release, police say the shooting happened Friday night during what are described as "interactions" between the vehicle's two occupants and the two officers involved.

Police say one officer's gun went off, striking the driver, who was outside of his vehicle.

The man, from Duncan, B.C., is listed in critical condition in Victoria's Royal Jubilee Hospital.

RCMP say the investigation into the shooting is being conducted by the Vancouver Island integrated major crime unit, which is led by officers from the Victoria police department.

The RCMP says the Commission for Public Complaints Against the RCMP has been advised of the shooting and has sent an observer to Duncan to monitor the investigation.