An Ottawa police officer has been cleared of wrongdoing in the April shooting death of a Montreal man on Highway 417.

The province's Special Investigations Unit (SIU) concluded that the unnamed officer was justified in using lethal force on Richard Bastien, 43, who brandished a revolver after being pulled over at Walkley Road on April 22.

According to the investigation, Bastien pointed the gun at two officers, one of whom fired back from inside his cruiser. One round struck Bastien, who simultaneously shot himself in the left temple, the SIU concluded.

An autopsy found that the self-inflicted blast was in fact the fatal wound. Bastien died of his injuries two days later at the Ottawa Hospital's Civic campus.

"The officer had reasonable grounds to believe that Mr. Bastien might shoot either him or another officer," SIU Director Ian Scott said in a Friday statement.

"The officer's reasonable belief was based upon the receipt of credible information that Mr. Bastien had just shot someone, was armed, and was pointing a firearm at him."

Ottawa police said Bastien's vehicle matched a description filed in relation to an attempted murder in the west end earlier that day.

Emergency crews had responded to a 911 call at a home on Bearhill Road in West Carleton, where 65-year-old Rainer Elsner was suffering from several gunshot wounds.

At about 6 p.m., police saw the vehicle spotted travelling eastbound on Highway 417 near Parkdale Avenue.

When the driver refused to pull over for police, a brief pursuit followed until the vehicle finally came to a stop. The driver then attempted to flee on foot before the fatal shots were fired.

The SIU is called in whenever police are involved in incidents involving the public that result in death or serious injury. Seven investigators were assigned to the case.