In 1857, several families in a wagon train were California-bound when they caught the eye of a group of Utah Mormons. The church members felt threatened by these people for some unspecified reason and decided to attack. So that they wouldn’t be recognized, they dressed themselves as Native Americans.
They fight lasted five days until the Mormons declared a truce. The families, being low on food and water, accepted the truce as well as the offer to be taken into Mormon protection. The Mormons took them far away as possible from their wagon and proceeded to murder and bury them.
At first, some Mormon leaders blamed Native Americans for this atrocity but later admitted that it was them. There is a monument in the meadow of the Utah Mormon church which the killers belonged to that commemorates those who were killed.