Mormon includes chapter headers when he begins sections that change sources. In this case, the ultimate source changed from Ammon to Aaron and Muloki. Their story had to have been recorded separately from Ammon’s, but the most logical explanation of where Mormon got these stories continues to be Alma the Younger’s personal record. Just as Mormon included stories from other sources in the book he created, Alma took the stories he either read or heard from the sons of Mosiah and added them into his personal record. As with the story of Ammon and King Lamoni, when the narration happens in the third person, it is probable that we are usually seeing Mormon copying what Alma had written.