Ideas for the main storyline

• The main plot I would like my movie trailer to be about, is a zombie invading a school looking for one Particular person but killing everyone who passes by. Because it is only a trailer, I don't want a continuous story, I want there to be a lot of good transitions, that will get the audience more hooked on what is going to happen, and don't want to give the ending away but maybe at the end, show a scene when the zombie finally finds that one person he has been searching for, leaving my trailer on that big cliff hanger.
• I am thinking that maybe a narrator wound make my video look all the more better, but I don't want a normal, human voice, I want a sort of unnatural and quite scary voice, to give my trailer that edge and make sound more like a horror trailer.