While it appears some people who immerse in horror imagery feel provoked to commit the same aggressive crimes, there is no evidence of a causal factor, and millions of people watch such films without feeling instigated to act.
Some people process external images into aggressive behavior. Others might gain catharsis, and still others remain altogether unaffected. A few become horror film makers or novelists. <|:-p
It's not easy to know what effect a specific film might have. Whatever results, research shows that it has more to do with the viewer than the material viewed. It stands to reason that violent imagery will affect certain people in a way that inspires them to act out. From the story that affects them, they acquire a frame and guideline, and sometimes even interpret the film as a license to kill. Not everyone will be thus affected
Among those who are, it's safe to say there is such a thing as a "Copycat Effect" when the portrayal of violence grips a person so firmly that he or she decides follow the details of that specific template.
Has the movie made him kill? No, but has it given him ideas and methods even victims. We can see such troubling incidents have occurred--and are likely to occur again.