For some people, horror movies just aren't that scary. Regardless of what's happening on the screen, these people are able to separate the fiction from reality, and they never fall under the spell of even the best horror films. But scary documentaries, especially those dealing with true crime, are a different story. The most terrifying true crime documentaries will scare even the most-hardened of horror movie fans, because everything that happens on screen actually happened in real life.

With true crime documentaries, there is no separating fact from fiction because there is no fiction, only facts. There's no telling yourself that "it's just a movie" because that's not true. It's not just a movie, it's documentation of something horrific that really happened to someone... and that could potentially happen to you. The 12 movies on this list are all horrifying in different ways, but most of them deal with killers. Not only that, but some of the crimes depicted in these films are so horrendous that it's almost impossible to believe that humans are capable of such behavior, and yet, they are. So if you're feeling brave and thinking that no movie can scare you, take a look at these 12 terrifying true crime documentaries.