Question:  "Cold North Killers: Canadian Serial Murder" is a 2012 Canadian non-fiction book that documents the lives of sixty Canadian serial killers one of whom was a former what?
Sentence (from "Russell Williams (criminal)"): From July 2009 until his arrest in February 2010, he commanded CFB Trenton, a hub for air transport operations in Canada and abroad and the country's largest military airbase.
Relevant evidence: No