No Budget Horror Film

What part of this video felt the scariest to you, and how could you use a similar idea in your own horror film?

I feel that the most scariest part from the video can be the video in general since  the vibe that generates, with their environment of tension and a feeling of desperation. After watching this video, I think what makes a video be scary is the scenario, sounds, background, lights, angles, etc. Causing scare and that mysterious place, however for my horror film, I'm gonna use a hallway as the video, because I feel that is a typical common use of a scary scenario.