Myself. It's much easier to describe "Joe retreats while shooting back and then dives in" instead of "Joe opens the door and suddenly a bullet pierces his eye and leaps out from the back of his head along with a piece of his brain". So, horror scripts should be longer...
Are you planning on making this yourself or making it for someone else to make? If it is the later, then you really need to think about conventional practices that has worked within the industry for the last hundred or so years.
While I'm not saying your wrong, selling a screenplay is hard, really hard. Selling a screenplay that doesn't conform to the norms is even harder.
There is a general concept in screenwriting. 1 page of script is approximately 1 minute on the screen. This does mean that you should not (not cannot) verbosely describe 10 seconds over 2 pages. If someone is considering buying your script, that part will feel bogged down and seem to drag on. In theory, you should alter your words and let the story flow at the correct pace of what you're trying to write.
This is just a rule of thumb. I've heard stories of people throwing scripts into the bin due to the fact that they had the wrong number of fasteners holding the script together (they believe that if you don't know the correct format, you have no chance to write a proper story, so why waste their time reading your script). How do you think they'll act if you present a 250 page script (about 3 times the industry norm) for your 85 minute horror story?
We're just talking norms here. There is nothing saying you have to do this or that. You can keep it to 250 pages. In the industry, time is money. You will need to find a way to convince producers or script buyers that spending 3 times the normal time to read a script is well spend on reading yours.
I suggest that you go to a script site on the internet and read a few scripts of your favorite movies, preferably ones that were successful, made within the last 5 years are in the same genre as what you're writing.
Good luck in your writing. You can take the advice or leave it.