The male passenger died in hospital shortly after being shot while riding in a 121 Cars taxi in Oldbury in the early hours of Sunday morning.
The driver of the cab was not injured but suffered severe shock after his car was ambushed in Dudley Road East just before 1.30am.
West Midlands Police launched a manhunt to track the gunman down but has so far failed to do so.
The force has also so far been unable to confirm the victim's age, with a spokesman saying there was no update regarding the investigation on Monday morning.
The only statement issued by the police regarding the killing was released on Sunday and said the investigation was in its early stages.
Dudley Road East was cordoned off throughout Sunday, with a blue forensic tent put up around the blue taxi involved.
Meanwhile neighbours told the Express & Star they were left in shock at learning that a murder had taken place in what is normally a quiet neighbourhood.
Councillor Rizwan Jalil, who represents the Oldbury ward, said he had visited people in the area who had been left in fear due to the attack.
Anyone with information is asked to contact police quoting log number 20/1126386/21.