A convoy of SUVs carrying American moms, kids, and babies in Mexico was attacked by drug cartel gunmen on Monday, killing at least nine passengers, including several children, authorities said.

The victims, many of whom had dual Mexican-American citizenship, were members of the extended LeBarón family and belonged to a Mormon offshoot group that had settled in Bavispe in the Mexican border state of Sonora more than 50 years ago, according to Mexican officials.

The three cars packed with kids and babies were heading to the Mexican state of Chihuahua when they came under heavy gunfire that left the vehicles burned out and riddled with bullets. Three women and six children, including 8-month-old twins, died in the horrific attack.

Mexican Security Secretary Alfonso Durazo said during a Tuesday press conference that the gunmen, who have not been identified, may have mistaken the group’s armed SUVs for those of a rival gang.

Durazo said eight people survived the attack, including six children who were wounded, five of whom have been transferred to hospitals in Phoenix, Arizona. Troops are still searching for a missing child, he added.

The LeBarón family has been targeted by cartel violence before, including in July 2009, when anti-crime activist Benjamin LeBarón and his brother-in-law were murdered by gunmen.

Kendra Lee Miller, who is related to many of the victims, told The Daily Beast the “first vehicle was found full of bullet holes and completely ablaze.” She alleged the women and children were “not caught in crossfire between two cartels, they were ambushed by one cartel from Mexico.”

“There was not ongoing battle or gunfire or anything at that point when these women went over this road,” Miller said. “They went over peacefully, the day was peaceful, and they were ambushed and attacked.”

“Three mothers in three vehicles, with 14 children between them, set out from LaMora, a small family community in the mountains of northeastern Sonora. Two of them to see family in Chihuahua, and one of them to pick up her husband from the airport in Phoenix,” Miller continued. “They never made it. They were ambushed by the Mexican cartels—shot, burned, and murdered in cold blood. These were innocent civilians, American citizens simply trying to live peaceful lives.”

On Tuesday, President Donald Trump tweeted he is willing to send reinforcements to help Mexico in “cleaning out these monsters” if they ask. Without mentioning that the victims lived in Mexico and are dual Mexican-American citizens, the president wrote on Twitter, “A wonderful family and friends from Utah got caught between two vicious drug cartels, who were shooting at each other, with the result being many great American people killed, including children, and some missing.”

The president added that the United States “stands ready, willing & able to get involved and do the job quickly and effectively” and that “the cartels have become so large and powerful that you sometimes need an army to defeat an army.”

Mexican President Andrés Manuel López Obrador rejected Trump’s offer during a Tuesday press conference, stating “it is not in agreement with our convictions,” but said he is planning to call Trump to discuss the massacre.

“The worst thing is war,” Obrador said, calling the incident “a regrettable situation.” He promised his government is doing “everything possible” to find and prosecute the perpetrators.

According to Miller, the dead include Christina Marie Langford Johnson, 29; Dawna Langford, 43; Trevor Langford, 11; and Rogan Langford, 2; Rhonita Miller, 30; Howard Miller, 12; Krystal Miller, 10; and 8-month-old twins, Titus and Tiana Miller.

“We lost 9 today. Right now we are waiting, for the morning, for answers, for justice,” Miller said.

Kenny LeBarón, a cousin of the women driving the vehicles, told The New York Times in an interview: “When you know there are babies tied in a car seat that are burning because of some twisted evil that’s in this world... It’s just hard to cope with that.”

Several family members survived the ambush, according to Miller, including 13-year-old Devin Langford, “who hid with six other siblings in the bushes and covered them with branches to keep them safe while he went for help.” Langford, who was uninjured, then walked for about 14 miles to La Mora, Mexico, where his family lives.

Worried her older brother would not come back, 9-year-old Mckenzie Langford, who was shot in the arm, also went to look for help with the other children but got lost, Miller said.

“Soldiers who’d by then arrived and the men of LaMora and nearby towns searched for two hours in the dark until they found her around 9:30,” Miller said in a statement.

Rhonita Miller was on her way to pick up her husband in Arizona airport with her family when they were attacked, while the others were going to Chihuahua to visit relatives, Miller said.

Fundamentalist Mormon communities in northern Mexico originated in the late 1880s and have long been unaffiliated with the mainstream church.

Those communities, which moved to Chihuahua and Sonora to practice polygamy, which was forbidden by The Church of Jesus Christ of Latter-day Saints, once included notable Mormon figures like Sen. Mitt Romney’s great-grandfather, Miles Park Romney. Polygamy has largely faded from the off-shoot communities.

In 1924, Alma Dayer LeBaron founded the Colonia LeBarón in the Mexican municipality of Galeana, Sonora—one of many family-run compounds created by Mormons excommunicated from the church.

The mainstream church currently has more than 1 million members in Mexico, making it the church’s largest population outside the United States, a church spokesperson confirmed to The Daily Beast.

While the church doesn’t recognize Colonia LeBarón, many in the community—including the more than 5,000 descendants of Alma Dayer LeBaron—still consider themselves Mormons, according to The Wall Street Journal.

“We have no way of knowing how many members of these Mormon communities live in Mexico because they are all not affiliated with one Mormon church,” Benjamin Park, assistant professor of history at Sam Houston State University, told The Daily Beast. “But I still say this is a tight knit community. These are all families that know each other and have connections going back a century now. It is not an outlier for this family to be well known and well liked in the area.”

According to a 2009 Seattle Times profile, Colonia LeBarón residents have mostly abandoned polygamy, raising large families that make money through agriculture and construction work.

The LeBarón family’s wealth has caught the attention of organized crime, making them targets of several tragic incidents, according to the BBC. In 2009, Erick LeBarón was kidnapped, and the community refused to pay for his $1 million ransom in hopes of preventing future kidnappings. LeBarón was eventually released.

Months later, his 32-year-old brother Benjamin—an activist who publicly led the campaign for Erick’s release—was murdered by over a dozen heavily armed men. Benjamin was abducted in July 2009 and beaten in front of his family before he was fatally shot 10 minutes from his home. His brother in law, Luis Widmar, was also murdered after running to get help.

The gunmen, who were dressed as police when they stormed the compound, left the two men next to a sign that read: “This is for the leaders of LeBarón who didn’t believe and who still don’t believe.”

In 2010, another family member, Julian LeBarón, published an article in the Dallas Morning News calling for Mexicans to stand up against organized crime.

“We have been threatened with death and violence at certain times if we went over certain public roads,” Miller said. “This is not just my community, the surrounding pueblos have been threatened and had people go missing.”

People saying they were relatives of the victims have posted tributes and details of the Monday ambush on Facebook, including one horrific video of the burnt-out SUV posted by a man who says his grandchildren were caught in the attack. His post also named 31-year-old Christina Langford Johnson as a victim whose 7-month-old baby was found alive on the floor of her SUV.