Social Learning Theory
Repeated exposure to violent acts on television encourages a copycat effect - especially amongst those who are considered vulnerable.
This kind of scaremongering often appears in the popular press and a number of cases have arisen where media texts have been blamed publically for people committing crimes - e.g. the Jamie Bulger case - although the police said the presence of certain videos in the killers' houses had no effect, in popular memory, the murder is till linked to the boys watching Childsplay III.
This is not too far away from Cultivation Theory. According to this, audiences are densensitised by repeated exposure to violence.