Murder in Admonishment

This case was a strange one; Detective Sergeant Kathleen Doyle was investigating what appeared to be an "admonishment" murder-a lower-level player in a turf war had been murdered to serve as a warning by a rival gang.
But the whole point of an admonishment-murder was to send a message, and in this case, it was unclear who was sending it, or even to whom it was being sent. And they'd another problem, in that Scotland Yard couldn't even seem to come up with a cause of death. . .