There are five guns in the game, and each gun is obtained in a different way:
1. After signing for the fat man, he will tell you where his gun is. If you don't want to help the fat man, you can ask the drunkard to sign for him.
Ruby can get her gun when she finishes the task.
3. The last one on the island.
There is a broken gun under the bookstore.
5. Crazy Marianne will give you one.