Ammon and his three companions were mistaken for the wicked priests of Noah who had been the reason why Limhi's people had been attacked by a Lamanite army (see Mosiah chapter 20 and 21:23). Also, Ammon had apparently approached the city when king Limhi and his guards were in the precarious position of being without the city gate (v. 10). Later Mormon records, the king himself did not trust his person without the walls of the city, unless he took his guards with him, fearing that he might by some means fall into the hands of the Lamanites (Mosiah 21:19). These were the two reasons why Limhi dealt with these fellow Nephites in such a severe fashion.