Here are five fast facts on this deeply devout community.

Breakaways

The Church of Jesus Christ of Latter-day Saints (LDS), or Mormon church, set up headquarters in Utah in 1847 when the territory was still Mexico.

The land passed to the United States the following year, after the Mexican-American War. But it remained a remote outpost where the Mormons were free to practice their faith on the shores of the Great Salt Lake.

That started changing after the US Civil War ended in 1865, when Washington began cracking down on a key Mormon tradition: polygamy.

Fleeing persecution, Mormons began arriving in northern Mexico's Sierra Madre mountains in 1875.

"That's how Mexico became the first country in Latin America where the Mormons settled," says Francisco Jara, an expert on Mormonism.

Many Mormons in Mexico have broken with the mainstream church, which has banned polygamy.

The LeBaron family, which lost six members in Monday's massacre, belongs to the Church of the Firstborn, a breakaway founded in 1924 in the Mexican state of Chihuahua. It has 5,000 members, according to community leader Julian LeBaron.

Polygamy

Joseph Smith, Mormonism's founder and one of its prophets, said he received a divine revelation on the godliness of "plural marriage."

The Mormon church endorsed polygamy until 1891, when it ended the practice under pressure from US authorities.

Around 40 Mormon breakaway sects still practice polygamy in Mexico, according to Jara.

But they are often discreet about it.

Community members told AFP that Dawna Langford, one of the victims, was her husband's second wife. But relatives were reluctant to talk to the media about it.

One million members?

LDS says there are 1.2 million Mormons in Mexico, making it the second-largest  Mormon community in the world after the US.

However, Mexico's last census counted 314,932 in 2010.

The Mexico City government attributed the difference to the fact that many Mormons in Mexico belong to breakaway groups and refuse to consider themselves part of the mainstream church.

Vigilantes

There is bad blood between northern Mexico's Mormons and the drug cartels that operate in the often lawless border region.

In May 2009, a criminal group kidnapped teenager Erick LeBaron in Chihuahua, demanding $1 million in ransom. The community refused, and LeBaron was freed.

After that, the LeBaron clan armed themselves and launched vigilante patrols. Most have dual US-Mexican nationality, which afforded them a degree of protection from criminal gangs wary of Washington's attention.

One, Benjamin LeBaron, founded a crime-fighting group called SOS Chihuahua that advocated for a crackdown on drug cartel violence.

According to Mexican media reports, the cartels in the area were incensed.

A group of 17 gunmen killed Benjamin and his brother-in-law in July 2009.

The family continues to help organize regular "peace caravans."

They reject the Mexican government's assertion their relatives were caught in the crossfire between warring cartels, saying they believe the group was deliberately targeted.

Water wars

According to Mexican media reports, the LeBarons have also been involved in disputes with local farmers over water, a scarce resource in the arid north.

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