Excellent use of atmosphere and tension. Reminds me of the Mist (S. King). I would love to see more (potentially).

I liked this piece! I thought it was paced well and you certainly have my interest if you decide to sequel!

However, I must say I have a few suggestions: I think you should cut out the first two lines (“Quiet. Too quiet.”) because in my opinion phrases like this seem very dated. Your third third line is where your story should start because the character then infers that things are too quiet by you saying muffled. Starting it there draws the reader immediately rather than giving them everything.

That being said, I think “Something wasn’t right” should be cut and instead start with the next line and so the flow would be better without, again, giving too much away. The reader will infer something isn’t right with dense fog and that way you don’t give away that there is a twist at the end.

At its core, this is a great piece and with small improvements, I think it could be even better. But if you love it like as is—it’s still an awesome piece!