This is an account I heard years ago in early morning seminary. It really intrigued me at the time, but I never knew the source of it. I have never heard it since that time and started to wonder the validity of it. I had searched for it in the past to no avail. Until today! I have found the source of the story of Moroni's fate after depositing the plates. For some reason I really believe this one. This is the story that first got me interested into the deeper parts of our religion. I hope you enjoy this as much as I do.
At a meeting at Spanish Fork, Utah Co., in the winter of 1896, Brother Higginson stated in my presence that Thomas B. Marsh told him that the Prophet Joseph Smith told him (Thomas B. Marsh, he being then President of the Twelve), that he became very anxious to know something of the fate of Moroni, and in answer to prayer the Lord gave Joseph a vision, in which appeared a wild country and on the scene was Moroni after whom were six Indians in pursuit; he stopped and one of the Indians stepped forward and measured swords with him. Moroni smote him and he fell dead; another Indian advanced and contended with him; this Indian also fell by his sword; a third Indian then stepped forth and met the same fate; a fourth afterwards contended with him, but in the struggle with the fourth, Moroni, being exhausted, was killed. Thus ended the life of Moroni.
-Charles D. Evans, LDS Church Archives, as quoted in H. Donl Peterson, Moroni: Ancient Prophet, Modern Messenger, p. 77.