Alma 25:5

and the remainder having fled into the east wilderness, and having usurped the power and authority over the Lamanites, caused that many of the Lamanites should perish by fire, because of their belief:

The rest of them ran away to the east wilderness. They took control over the Lamanites there. They burned many Lamanites to death because of what they believed.

The few survivors fled deep into the eastern wilderness. There they seized power over some Lamanite groups and began executing any who believed in God—burning them alive for their faith.