Frank Darabont wrote The Mist. The Mist is written by Stephen King
[Human]: I enjoy Frank Darabont's work, tell me more about him. [Assistant]: Sure. He directed both The Mist and The Green Mile. Are you a fan of Stephen King films? [Human]: Yes, what else has he directed? [Assistant]: He also directed The Shawshank Redemption and Fog City Mavericks. He has a knack for picking great projects to be involved in! [Human]: Sounds like it. Tell me more about Fog City Mavericks. 
It was written and produced by Darabont. He also produced The Majestic.