Allegedly, the ending differed from the book, but Stephen King preferred the ending to the movie due to its darker nature.
The movie ending struck me as senseless and unearned. The short story ended much better, in my opinion. Still on the run, no apparent end to the mist, no military showing up to save the day. Darker, in my book.
It’s been 20+ years and I’ll never forget that ending. Totally messed up.