* A warning: The bullet is a message to the deceased's family or associates that they are being watched and that they are not safe. It's a way of saying "We're coming for you next."
* A display of power: The act is meant to intimidate and show that the gangster is in control. They are not afraid to use violence and want everyone to know it.
* A revenge gesture: The bullet can symbolize a final act of retribution against the deceased for something they did. It's a way of saying "You're not truly gone, we're still holding a grudge."
* A reminder of the gangster's ruthlessness: The bullet is a symbol of death and violence. It's meant to shock and remind the audience that this gangster is dangerous and not to be messed with.
It's important to remember that this is a fictionalized scenario, and it's not meant to be a realistic depiction of actual criminal activity.
Let me know if you'd like to explore this trope further in the context of a specific film or story!