Here's why:
* "Old shack": The word "shack" suggests a dilapidated structure, and "old" emphasizes its age and potential decay.
* "Looked as if it were about to collapse": This phrase creates a sense of impending danger and instability. It paints a picture of something fragile and vulnerable, likely to give way at any moment.
This combination of imagery evokes a sense of unease and foreshadows potential misfortune.