A man was found fatally shot in this black BMW in the 1800 block of 4 Street S.W. early Sunday morning. He died in hospital a short time later. ((Kirk Heuser/CBC))

Calgary police are looking for witnesses after a man was found shot in a luxury car in the city's southwest early Sunday morning.

Police were called to the area of 18 Avenue and 4 Street S.W. at about 2:30 a.m. after reports of gunshots.

When officers arrived, they found a wounded man, believed to be in his twenties or thirties, slumped behind the wheel of a black BMW stopped in the northbound curb lane in the 1800 block of 4 Street S.W.

The man was taken to hospital, where he died a short time later.

Police say a woman in the passenger seat escaped without injury, and a second man, who police later determined was the victim's brother, turned up at a local hospital where he was treated for a gunshot wound.

Insp. Keith Pollock with the Calgary Police Service said investigators are interviewing a number of potential witnesses.

"This is a very busy intersection at that time of night, so there is a lot of people we are talking to, and so hopefully, it will all start to sort out who actually saw the incident and who saw things that are related," he said.

Police said they are interested in speaking with two women who were seen talking to a man behind a building on the east side of the 1800 block of 4 Street S.W. just before the shooting.

An autopsy is expected to take place Tuesday.

Anyone with information is asked to call Calgary police at 403-266-1234 or Crime Stoppers at 1-800-222-8477.

With files from the Canadian Press