One Piece Chapter 4, page 17-18: Chapter 4: The Great Captain Morgan

Luffy grabs Helmeppo, saying he's been looking for him, and drags him inside the fortress while Helmeppo screams for his father's help. Morgan orders his men to kill all the rebels. Down in the parade ground, Coby runs up to Zoro to untie him. Zoro warns Coby that he's being reckless and will get killed, but Coby bravely declares that he can't stand to see the Navy act improperly and wants to become a proper Marine, just like Luffy is going to be the King of the Pirates.

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.