[1] Mackey graduated from high school in Scarborough, Ontario and thought of becoming a chemist or builder but, with work difficult to find during the Great Depression he found employment as a milkman when Toronto police sergeant Michael Byrt said to the young Mackey, "Lad, why don't you join the force?
"[2] Mackey joined the original Toronto Police Department in 1936, "Jim was the 20th of 20 men taken on," his wife, Anne, later recalled.
[1] He walked the beat, then became a detective[2] and rose to the rank of junior inspector when, in 1958, he skipped two ranks to be appointed to be chief of police of the newly created Metropolitan Toronto Police following the suicide of Chief John Chisholm.
[1] In the 1960s, he was successful in stopping mobsters from Buffalo, New York from establishing a foothold in Toronto.
[1] Mackey retired to Bracebridge, Ontario where he died at the age of 95.