Megosztott hang

This happened last year when I was helping my friend move some stuff into a storage facility just outside town. It was one of those places with long rows of units… metal doors… and not a lot of lighting at night. We got there kind of late. Around 9:30.There were only a few cars in the lot. Didn’t think much of it. We unloaded everything pretty quickly. Maybe 20 minutes. As we were finishing up… I noticed something. One of the units across from us was slightly open. Not wide. Just enough to see.