Mountain Meadows Massacre

The Mountain Meadows Massacre (September 7–11, 1857) was a series of attacks during the Utah War that resulted in the mass murder of at least 120 members of the Baker–Fancher wagon train. The massacre occurred in the southern Utah Territory at Mountain Meadows, and was perpetrated by settlers from the Church of Jesus Christ of Latter-day Saints (LDS Church) involved with the Utah Territorial Militia (officially called the Nauvoo Legion) who recruited and were aided by some Southern Paiute Native Americans.

Source: Wikipedia — Mountain Meadows Massacre (CC BY-SA 4.0)