I have tried making horror stories, and I won't give up on doing them. To me, to write a horror story [not like King since, face it, we will never write stuff like him] is to write something that will not only captivate the readers, but also make them feel a certain way at any given time.
While Zenar 24 isn't that much of a horror story (Unless you count the mc being a monster), I did once write another Zenar story from the perspective of humans. In it, I showed just how scary Zenars are to everyone else, and always tried my best to give the readers a sense that there is no hope, and no chance of fighting back. Survivors have a safe place? Bam! A Single Zenar finds it, breaks in, and kills someone. Things seem safe? Bam! Zenar has been spotted. (It's important to make sure that there is some downtime and some cases where the mc and their group makes it through something)
In another story of mine, Your God, I base it off classic rpg horror games like Corpse Party, that one Blue Oni game, and etc. An old student returning to her old school years after a terrible massacre occurred, claiming the lives of most of the students there. The atmosphere I am going for in this one is more tension than hopeless. The school is now owned by the monsters that used to be the dead students, with the school itself seemingly going on forever. The difference between this and the other Zenar story is what the mc is doing.
In the Zenar story, it is about a group of survivors trying to survive against a deadly infection that creates planet-ending threats on mass. In Your God, the mc is trying to make it through her old school to find a missing friend. What the goal is for the mc, or group, is important in how you're going to make a horror story.
I can go on and on about more types, but I think ya get the gist by now. Make your readers feel a certain way, and make the horror fit the goal of the mc.