From Wikipedia

Crime Inc.
Episode Five

The Mob at Work

In order to be invited into the American Mafia and become a member one must perform a series of tasks, such as committing murder for the family and not for ones own personal benefit. When the boss decides to let a member into the family one will be part of a ceremony, involving the drawing of blood, swearing an oath over a gun or holy picture, and obeying the rules of the organization. In New York City, the mafia created customs and traditions which the members have to follow. If one breaks any of the rules they can be killed by another member of the family and usually the murder is committed by the people closest to that person.