Nothing! The Church of Jesus Christ of Latter-day Saints (commonly called the "Mormon" church) has been growing steadily since it began in 1830 with about 40 members. There are now nearly 14 million baptized members of the Church worldwide.
Perhaps you are thinking of the Mountain Meadows Massacre? I wouldn't really say that "The Mormons" participated, as it was only a small group of Mormon men, not ALL Mormons, that were involved.
In Mountain Meadows, a small group of Mormon men and Paiute Native Americans, which made up the local militia, ambushed the Fancher-Barber wagon train. Everyone over 8 years of age (about 120 people) was killed. The Fancher-Barber train was from Arkansas and traveling to California.
While it is admittedly inexcusable to massacre a wagon train, historians note that this group from Arkansas was traveling through a wild part of Utah Territory at a very tense time during the Utah War. Local militias were on alert and ready for attack, as Presdent Buchannan had sent unwanted troops to come 'lay down the law' in the territory. The combination of the tense war situation and the fact that it was a group from Arkansas that had previously murdered Joseph Smith, the Mormon Prophet, is probably what incited this militia to attack the wagon train.
The Mormons used it as a code meaning "Killed"
I don't know who "he" is, but I don't think there has ever been a killer or a deadly event in which only Mormons were spared from death - so I guess the answer is yes.
You are thinking of Joseph Smith, Jr. He and his brother Hyrum were shot and killed by a mob in Carthage, Illinois on June 27, 1844.
Since Mormonism began in 1830, the main challenge Mormons have faced is criticism for their beliefs. At times this has caused violence, and some have even been killed for their beliefs, but for the most part it is just a general unacceptance.
Historically, Mormons were persecuted by being kicked out of their homes and chased out of their settlements, some were even killed. Today, persecution against Mormons is much less brutal. Typically they are only persecuted by harsh words and negative attitudes, although occassionally their homes or churches are vandalized. You can check out some examples of how Mormons have been persecuted historically and in modern times at the "Related Links" below.
Of the 13,824,854 members of the Church of Jesus Christ of Latter-day Saints (the "Mormon" church) worldwide, 7,785,947 live outside the United States. That is, 56% of all baptised Mormons live outside the U.S. Nations with quite a few Mormons are: Canada 179,801 Mormons (1% of Mormons are Canadian, 0.5% of Canadians are Mormon) Samoa 69,224 Mormons (0.5% of Mormons, 39% of Samoans) Tonga 55,173 Mormons (0.5% of Mormons, 53% of Tongans) Mexico 1,197,573 Mormons (8.7% of Mormons, 1% of Mexicans) Guatemala 220,296 Mormons (1.6% of Mormons, 1.6% of Guatemalans) El Salvador 105,501 Mormons (0.8% of Mormons, 2% of El Salvadorians) Hondouras 136,408 Mormons (1% of Mormons, 2% of Hondourans) Brazil 1,102,674 Mormons (8% of Mormons, 0.6% of Brazilians) Chile 561,920 Mormons (4% of Mormons, 3.3% of Chileans) Peru 480,816 Mormons (3.5% of Mormons, 1.7% of Peruvians) Philippines 631,885 Mormons (4.6% of Mormons, 0.7% of all Philippinos) UK 186,082 Mormons (1.3% of Mormons, 0.3% of all UK) Australia 126,767 Mormons (0.9% of Mormons, 0.6% of Australians) New Zealand 100,962 Mormons (0.7% of Mormons, 2.4% of all New Zealanders) To compare, the United States has 6,038,907 Mormons. That's 44% of Mormons and 2% of all Americans. But you can find Mormons in nearly every nation of the World! The "Related Link" below has a great population statistics map related to Mormon Church membership.
I don't know that there is any specific number counted, perhaps about 50 have been killed directly due to their religion, and thousands have been killed while attempting to escape persecution (as in the case of the Mormon pioneers).
Mormons are christians!!!!!
This question is based on an incorrect supposition. Not all Mormons are liars; most Mormons are not liars.
many Mormons are minors
Mormons are Christians.
Utah was settled by Mormons.