Alma 51:19

And it came to pass that there were four thousand of those dissenters, which were hewn down by the sword; and those of their leaders which were not slain in battle, were taken and cast into prison, for there was no time for their trials at this period;

Four thousand of those who refused to fight were killed by the sword. The leaders who were not killed in battle were taken and put in prison. There was no time for trials right then.

Four thousand dissenters fell by the sword. The surviving leaders were arrested and thrown in prison—there was no time for trials right now.