A North Dakota family was part of the nine U.S. citizens killed in a Mexican highway ambush.

According to family member Heather Miller, five of those slain lived in the western North Dakota town of Williston.

Rhonita Miller, 30, Howard Miller, 12, Krystal Miller, 10, and 8-month-old twins, Titus and Tiana Miller were from Williston.

Local media described the killings as a highway ambush that happened in the Mexican border state of Sonora late Monday.

Two family members Valley News Live spoke with, Heather Miller and Lafe Langford, said the murders were done by Mexican drug cartels.

Miller said a motorcade of three vehicles came under attack while traveling to the airport.

The family lives in North Dakota part time and has a vacation home in a Mormon community in northern Mexico.

Congressman Kelly Armstrong, R-ND, told Valley News Live his office has been in touch with the State Department about the attack.

Rep. Armstrong added, "My heart breaks for this family. The loss and horror is unspeakable. Those who perpetrated this evil must be brought to justice. We are working to gather as much information as we can to ensure that that the survivors are being cared for in the best way possible under these circumstances."

Senator John Hoeven, R-ND, also sent us a statement on the killings.

"Mikey and I send our deepest condolences to family and friends of the Miller family. The senseless killing of these women and children is despicable,” Sen. Hoeven said. “The ruthless violence of the drug cartels in Mexico is abhorrent, which is why our nations should work together to stop the violence at the border."

Valley News Live will be speaking with Sen. Kevin Cramer, R-ND, concerning these deaths.

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At least nine U.S. citizens — including six children — were killed in what local media described as a highway ambush in the Mexican border state of Sonora late Monday, a family member told NBC News.

The dead included 8-month-old twins, said Kendra Lee Miller, who is related to many of the victims. Some of the eight survivors — all children — sustained serious injuries.

Miller added that the victims lived in La Mora, which is about 75 miles south of the U.S. border.

Miller named the victims as Christina Marie Langford Johnson, 29, Dawna Langford, 43, and Trevor Langford, 11, and Rogan Langford, two-and-a-half. Also slain were Rhonita Miller, 30, Howard Miller, 12, Krystal Miller, 10, and 8-month-old twins, Titus and Tiana Miller.

Earlier another relative of one of the victims, Willie Jessop, told NBC News on the phone from Utah that a number of people were traveling in a motorcade consisting of several families when they came under the attack.

Jessop said three of the cars were shot at and one of them was set on fire based on the information he has been receiving from other family members at the scene.

He added that they have been trying to mobilize Mexican federal officials and have been in contact with the FBI.

“Everyone is in so much shock," he said. "It's just unbelievable and there's just no way to comprehend it."

Miller also recounted dramatic details from the survivors, some of whom sustained serious injuries, including a 9-month-old child who was shot in the chest and a 4-year-old shot in the back.

Devin Langford, 13, she added, was not injured but walked around 14 miles to La Mora for help after hiding his injured siblings in bushes and covering them with branches.

A bullet grazed Mckenzie Langford, 9, in the arm but she also went to find help after Devin did not come back. Miller said Mckenzie got lost and walked for hours in the dark before she was found by search parties.

Mexico has been hit by a wave of attacks in recent weeks, shocking even for a country used to more than a decade of intense drug war violence. The most notable incident was a military-style cartel assault that forced the government to release a leader of the Sinaloa Cartel in October.