The footage shows the man with short, dark hair, a beard and moustache leaving the victim's building last August, and police hope a member of the public can identify him.
RCMP say the man seen wearing jeans and carrying a black bag could have worked with two other men who have already been charged in the case.
The mystery man is one of two unidentified suspects spotted by a witness who called police while watching four men force the victim, at gunpoint, into a car where his little boy was already strapped into a car seat.
Officers stopped the vehicle a short time later and released the child and his dad.
Nineteen-year-old Raymond Truong and 27-year-old Ryan Stalker are charged with kidnapping, while the search for the other two suspects continues.
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