Muhab Sultanaly Sultan, 23, of Calgary is wanted for second-degree murder in connection with the shooting and remains at large as of Friday evening.
Jeremy Cook over cellphone an 'extreme' case, say police
Police released Sultan's picture and warned anyone who sees him to call 911 right away and not approach the man.
London police are also looking for a second suspect, described as a black male with very short hair who was wearing a black jacket or shirt and a fitted hat.
A third man, who exited the vehicle just before the shooting, is being asked to contact police and identify himself.
Cook, 18, was gunned down at about 5:15 a.m. ET on Sunday, police said. The Brampton, Ont., teen's body was found behind a strip mall near Huron Street and Highbury Avenue in the city's north end. He had multiple gunshot wounds.
Cook had left his smartphone in a taxi and traced it electronically to an address on Highbury Avenue, police say.
When Cook and a relative went to the address, he was confronted by three men in a car. Police said that when Cook tried to retrieve his phone, the vehicle began to drive away, prompting him to grab on to the driver's side door. That's when the fatal gunshots were fired, police said.