Papercuts - "The Mist"

from Goodreads:
A man staggered into the market . . . 'Something in the fog!' he screamed. Following a freak summer storm, David Drayton, his son Billy, and their neighbour Brent Norton join dozens of others and head to the local grocery store to replenish supplies. Once there, they become trapped by a strange mist that has enveloped the town. Violent forces concealed in the mist are starting to emerge. And there is another shocking threat from within - one group of survivors, led by a religious zealot, is calling for a sacrifice. Now David and his son must try to escape. But what's outside may be even more dangerous. This exhilarating novella explores the horror in both the enemy you know - and the one you can only imagine.