Danites

Danites, or "destroying angels," were an organised band of Mormons intended to prevent the entry into the Mormon territory in Utah of other than Mormon immigrants. Shocking stories were told of the atrocious cruelties perpetrated by them on inoffensive non-Mormon immigrants. The worst of these - the massacre of 100 persons at Mountain Meadows Creek - was committed in 1857, but not punished till 1877, when a leading Mormon, John D. Lee, was convicted of participation in it and shot. The opening of the Pacific Railway made such attempted prevention hopeless.