Some of the attacking Lamanites become cognizant of the slaughter. There is no glory in such a battle, and warriors raised on the concept of the glory of combat would see this as repugnant, even if they have no other moral ground for halting the killing.
Textual: The connection between verse 23 and 24 is somewhat awkward. It would appear that verse 23 is heading is a particular direction, and that verse 24 somewhat pulls back and clarifies. This is not the type of mistake we saw above. In this case, the construction could also be intentional. Thus we are unable to make any indication of whether this particular construction reflects Mormon or Joseph. A case could be made for either. In the absence of any other evidence, it is perhaps best to make the assignment to Mormon.