The horror genre in movies has no set of rules when it comes to scripts. Over the years, however, with every innovative way to scare having been explored, we, the audiences, have turned quite the experts in predicting the end of every horror story that we see on a screen. This may or may not be a good thing, depending on the condition of your heart, but that does not stop us from swarming the theatres whenever a horror film is released.
Actually, if you have not watched the trailers too closely, you would not have known that 3 AM is a horror movie. It looks more like a romantic ....