There are many who are killed, and the leaders of the insurrection are imprisoned. It would appear that some version of trial was expected, because Mormon is cautious to tell us that this rapid imprisonment was justified by the circumstances, something he would not have needed to do unless he expected his readers to have the conception of the trial.
The number four thousand is a suspicious number. Any time the number four appears in a Mesoamerican context that is not a calendar, it should be immediate suspicious as an invented number that is important for its symbolic content more than as a count. The number four was the number of completion in Mesoamerican cultures, and 4,000 deaths could easily be seen as a ‘complete’ destruction of the dissidents (see also the article on Counts and Estimates in the Book of Mormon).