At least six children and three women living in a faith-based community of U.S. citizens in Mexico were shot to death Monday in the northern part of the country, and six more children were wounded and one missing after their convoy came under fire during a brazen daylight ambush believed to have been carried out by gunmen affiliated with the cartels.

Alfonso Durazo, Mexico’s top security official, confirmed the six deaths, adding that six more children were wounded in the attack, with five transferred to hospitals in Phoenix, Ariz. One child is still missing.

Relatives said the victims live in the La Mora religious community in northern Mexico, a decades-old settlement in Sonora state founded as part of an offshoot of The Church of Jesus Christ of Latter-day Saints around 70 miles south of Douglas, Arizona.

They said the group was attacked while traveling in a convoy of three SUVs. Durazo said the gunmen may have mistaken the SUV convoy for rival gangs.

The victims were all reportedly dual Mexican and U.S. citizens and were traveling back to the U.S. when they were ambushed, according to Utah’s KUTV.

Among those killed were Rhonita Maria LeBaron and her four children, including twin 6-month-old babies and two others, ages 8 and 10. Her burned-out bullet-ridden SUV was reportedly found outside the town of Bavispe, where the settlement is located. Relative Lage Langford Jr. shared a video on Facebook that showed the SUV.

Relatives claim that cartel members kidnapped surviving church members after the initial shootout.

Langford Jr., who grew up in the settlement but now lives in the U.S., told the Salt Lake Tribune the bodies of the two other mothers in the group – 43-year-old Dawna Ray Langford and 31-year-old Christina Marie Langford – were found in a separate location later Monday. A third relative said a 4-year-old girl and a 6-year-old boy were also killed, bringing the death toll to at least nine.

Langford Jr. told Fox News: “It’s just huge. It’s just absolutely unimaginable. This is the absolute worst nightmare for our entire existence in Mexico…and we never thought it was possible.”

Jhon LeBaron, another relative, posted on his Facebook page that his aunt and another woman were dead. He also posted that six of his aunt’s children had been left abandoned, but alive, on a roadside.

In a series of tweets Tuesday morning, President Trump hit out at the “monsters” who perpetrated the act.