QUEEN CREEK, Arizona -- The message popped up on the family WhatsApp thread just after noon."Howie's wife and four kids have been killed," it said. "Christina and Donna and their kids are not accounted for. Were traveling with them."Aaron Staddon married into the diaspora of Mormon families who have long lived in the rural valleys of northern Mexico, and he shuddered when he read through the haunting thread of messages coming from south of the border."My heart just sank," said Staddon, 44, who owns a swimming pool company outside of Phoenix. His wife, Leah Staddon, grew up in La Mora, where about 200 members of their extended family have built a thriving farming community in the Mexican state of Sonora. "This is the kind of nightmare that just floors you."The news, arriving Monday in a series of text messages, voice texts and short, horrifying videos, kept getting worse: More than a dozen members of their family had been attacked by gunmen in Mexico who had opened fire on their SUVs. By the time it was over, nine people were dead, and six others, including several children, were injured."Innocence is shattered right now," said Joe Darger, another relative who quickly called an emergency family meeting at his home in Utah. "We don't even know what to do about funerals."The extended family struck by Monday's violence has long roots in the broader community of fundamentalist Mormons who first took up residence in Mexico's northern border regions in the late 19th century.Initially, the family's patriarch was part of a wave of religious rebels who headed south to practice polygamy, once it was banned by the Church of Jesus Christ of Latter-day Saints.Today, with descendants scattered across the American West, those living in La Mora are successful pecan, chile, alfalfa and pomegranate farmers, raising children who have dual American and Mexican citizenship. Only a few still practice plural marriage, but they continue to live as an observant religious community deep in some of Mexico's most turbulent borderlands."It was a great place to raise kids," said Staddon, describing how he and his wife would pack their five children into their SUV each year for the eight-hour drive from Phoenix to La Mora.On Tuesday, several of the injured children were flown in for treatment at a hospital in Tucson, Arizona, and family members tried to piece together what had gone wrong. A photo quickly traveled from phone to phone: There was 8-year-old Cody Langford, one of the surviving children, on a hospital bed, his head swaddled in bandages, a thin shoulder peeking out from under a white blanket.Then came a video showing the youngest survivor, 7-month-old Faith, shrieking as adults tried to comfort her.The WhatsApp text that said "Christina and Donna" were unaccounted for was followed up with news that Christina Langford Johnson, 31, and Dawna Langford, 43, were among the dead."The whys we don't know," said Darger, growing emotional as he recounted the pain of waiting for news. "Did they specifically attack La Mora?"Staddon said he had always been surprised at the contrast between the large homes that the Americans and their descendants had built in northern Mexico, and the poverty that surrounded them.The American families got along well with their neighbors, he said. But the families' location in the path of Mexico's gun violence has cost them dearly in the past: Two family members were kidnapped and murdered by people believed to be drug cartel members in 2009.More recently, Staddon said, family members have been facing new challenges, including the control of gasoline distribution by criminal gangs, which has made farming operations more difficult. Cartels in Mexico seem to be looking for new sources of revenue to make up for losses related to the legalization of marijuana in parts of the United States, he said.Family members have begun returning to the United States. Some of them are no longer willing to adhere to the community's strict religious practices, Staddon said, but many are also wary of the violence that is once again on the rise. Some families had recently traveled north to Arizona to scout out possible purchases of farmland."But an exodus takes a little time to organize," Staddon said. "It's tough to leave a place where your family's invested so much."As the text and Facebook messages continued to flow in Tuesday, those who have returned to the United States, or never left, communicated almost nonstop over telephones and social media.David Langford, 29, who grew up in La Mora but now lives in North Dakota, said his sister, Christina Maria Langford, was one of the women killed in Mexico. Those who committed the assaults were "ungodly," he said, "some of the most wicked men on the face of the planet."A relative in Seattle, Amber Bostwick, said she was simply shocked."I would hope that this would bring about more safety from elected officials in both Mexico and America," said Bostwick, 35, a homemaker whose biological father still lives part of the time in Mexico."Everybody's on edge. Everybody's suffering," said Lynn Wariner LeBaron, a family member who works in Denver.Long unaffiliated with the mainstream church, fundamentalist Mormon communities in northern Mexico originated in the late 1880s, when a number of families moved to the states of Chihuahua and Sonora. The settlers who put down stakes included Miles Park Romney, the great-grandfather of Sen. Mitt Romney, R-Utah, and the party's presidential nominee in 2012.The families of La Mora are independents who broke off from the larger fundamentalist movement in the 1950s, though some share the same name as distant family members in the separate LeBaron community, said Lindsay Hansen Park, a historian who produces a podcast on the history of polygamy.Over time, the communities have connected through marriage and intertwined families. Some families today are monogamous, and others practice plural marriage."They practice their own brand of Mormon theology," she said. "They don't follow a group or a leader."Three family branches make up the group -- the Langfords, the Stubbs, and the LeBarons -- but the Langfords were the ones primarily victimized in Monday's attack, she said.The LeBaron community suffered decades of horrifying violence in past decades, some of which was caused by internal strife.In the 1950s, Joel LeBaron had helped establish the community in northern Mexico in order to pursue a polygamous Mormon life, said Ruth Wariner, who was the 39th of 42 children Joel had with six wives. She now lives in Portland, Oregon, but maintains close contact with family members in Mexico.But Joel's brother, Ervil, split from the church to start his own following who believed in blood-atonement -- in some cases violence -- as punishment for sin, ultimately resulting in Joel's killing, Wariner said. Ervil was suspected in a series of killings of rival religious leaders.By the early 1990s, in the years after Ervil LeBaron died in prison, Wariner said things grew more peaceful until drug traffickers emerged as a new threat.In more recent years, the LeBaron community had established a sort of truce with the cartels, Wariner said. They had an understanding, she said, that the community would not go after the traffickers if the traffickers left the community members alone. She said the killings were a surprise because there did not seem to be a cause for such an attack."Things seemed to be getting more peaceful," Wariner said.But one woman who asked not to be named out of fear for her safety said families traveling between the LeBaron and La Mora communities had been getting stopped lately by cartel members who asked where they were going and what they were doing.They have generally been respectful, and did not seem to care about ordinary travel, the woman said.But David Langford, who grew up in La Mora, said cartel members recently had been warning people to "stay off" the road between the La Mora and LeBaron communities at night."We did," Langford said. It was a big change from the "peaceful" place that northern Mexico was when he grew up, he added."What just happened has never happened in this valley -- ever," he said. "We've been traveling that road for 50 years."This article originally appeared in The New York Times.(C) 2019 The New York Times Company