A person commits robbery when he or she unlawfully takes personal property from the person of another or in his or her presence against his or her will by the use or threatened use of immediate force, violence, or fear of injury to that person or his or her property or the person or property of anyone. Such force or fear must be used to obtain or retain possession of the property, or to prevent or overcome resistance to the taking; in either of which cases the degree of force is immaterial. Such taking constitutes robbery whenever it appears that, although the taking was fully completed without the knowledge of the person from whom taken, such knowledge was prevented by the use of force or fear.