Redaction: Mormon certainly had a source for this story but is crafting his own account from them. In the official history, the relation between Nephi’s prophecy and the murder may not have been as prominent as Mormon makes it, or the sequence may have been different. Here Mormon is dealing with the murder, not Nephi’s role, since the actual murder would have been reconstructed after the murderer’s apprehension. Mormon is drawing from the official record and already knows who the culprit is.
According to this account, the murder must have occurred when the chief judge was accompanied by only a few servants, since they must leave the room to summon others to see the corpse. Furthermore, the murder must have been committed while Nephi was addressing the crowd. Mormon must narrate sequentially events that happened simultaneously. He chose to emphasize Nephi’s prophetic role, then recapitulate past action to bring it into present time. The fact that Mormon coordinates the murder to Nephi’s actions, not vice versa, clarifies that his editorial focus is on Nephi and his prophecies. He recounts the murder because it confirms that Nephi is a true prophet, not because Mormon is interested in the intricacies of the Gadianton government.
By stating that this murder was committed under “a garb of secrecy,” Mormon is alerting his readers that this is another Gadianton murder for political power.