One Piece Chapter 4, page 18: Chapter 4: The Great Captain Morgan

Zoro is stunned to hear that Luffy wants to be the King of the Pirates, asking if he even knows what that means. Coby smiles, saying he was shocked too, but knows Luffy will succeed or die trying. Suddenly, a loud explosion echoes from the fortress. Luffy is seen running through the halls, dragging Helmeppo behind him while demanding to know where Zoro's swords are. Marines chase after them.