I think that horror is one of the most flexible genres. You can do anything you want, and often, little or no research is required. I do have a tip for you, though.
It’s easy for a horror story to sound like a catalog of events. Each one is scary, but if you pile terrible event upon terrible event, it starts to dull the horror you’re trying to create in your Reader’s mind. Therefore, I suggest breaking it up with some normal life. Maybe something really bad happened last year. Your character could have flashbacks and dreams, but you can intersperse them with scenes of making dinner, making love, or making movies. More bad things are probably scheduled to occur in your story, but I suggest introducing them slowly, build the suspense, and keep right on including normal stuff so that your Reader is left guessing when something horrible might go down.
Next week’s writing post will be on Wednesday, August 5, and I haven’t selected a topic yet. It may be about a genre, or it might be a general writing post.