A family from Oklahoma, returning to the U.S. after visiting relatives in Mexico, was attacked by gunmen, and one relative says "bullets were everywhere" during the fatal incident in the sparsely traveled area near the Texas border,

Oscar Castillo López, 13, was killed, while a 10-year-old relative was among four wounded in the attack, according to the attorney general’s office in the state of Tamaulipas.

Jose Mendoza, one of the family members who survived the attack, told FOX25 that on Saturday night, the family was on a two-lane highway paralleling the U.S.-Mexico border in Ciudad Mier.

OKLAHOMA TEEN KILLED BY GUNMEN IN MEXICO, FAMILY ATTACKED

Mendoza, said he was driving a car with his niece and her two sons inside when they started being chased by another vehicle. The family was returning from a holiday visit to relatives in the state of San Luis Potosi in vehicles with Oklahoma license plates.

The deadly attack happened Saturday night on a two-lane highway paralleling the U.S.-Mexico border in the township of Ciudad Mier near the Texas border. (Bing/Fox News)

An SUV passed the family, then cut Mendoza's car off, causing a collision. He stopped and gunmen in the SUV opened fire, according to a statement from the state of Tamaulipas security coordinating group. The gunmen escaped in another vehicle.

"I was praying. Praying, praying, praying," Mendoza told FOX25 Monday. "I didn't want to die right then."

He said that his nephew was among those shot and that one person died. "We tried to stop the bleeding."

Luis Enrique Orozco, a deputy in the Nuevo Leon state prosecutor's office, said another boy was in critical condition along with a 48-year-old man. A 42-year-old woman was in stable condition, he said. The relationship between the adults and the children was unclear, but Orozco said the two wounded adults were siblings.

TheTamaulipas attorney general's office said the slain 13-year-old was a U.S. citizen and that the parents were permanent residents of the U.S.

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The highway where the attack took place is considered to be in a high-risk area contested by Mexican drug cartels. It connects the city of Mier with Nueva Ciudad Guerrero, on the banks of the Rio Grande across the U.S.–Mexico border from Falcon Heights, Texas.

For years, Ciudad Mier was the uppermost edge of the Gulf cartel’s control and Nueva Ciudad Guerrero was the limit for the Nuevo Laredo-based Zetas. Between them sits uninhabited land, according to The Associated Press.

A view of the University Hospital in Monterrey, Nuevo Leon state, Mexico, Monday, Jan. 6, 2020, where the survivors of an attack on a family in a car with Oklahoma license plates are being treated. (AP Photo/Antonio Escobar)

In 2010, after the Zetas split from the Gulf cartel and established themselves as an organized criminal power through prominent displays of graphic violence, Mier became a battleground for the two cartels and most of its residents abandoned the quaint colonial town.

More recently, however, the Zetas’ splinter group known as the Northeast cartel has been as far downriver as Mier, Miguel Aleman and Camargo, well into what was traditionally the Gulf cartel’s territory.

Photographs from Saturday night’s scene showed the Northeast cartel’s Spanish initials — “CDN” — scrawled on the back window of one of the vehicles.

A damaged pick up marked with the initials C.D.N., that in Spanish stand for Cartel of the Northeast, is on the streets after a gun battle between Mexican security forces and suspected cartel gunmen, in Villa Union, Mexico, Saturday, Nov. 30, 2019. (AP Photo/Gerardo Sanchez)

Similar vehicles belonging C.D.N. of the Cartel del Noreste, or Cartel of the Northeast, were used in a November ambush in the small town of Villa Union.

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In a statement, the State Department confirmed that one U.S. citizen was killed and two injured.

"We offer our sincerest condolences to the family on their loss, and we are providing them all appropriate consular assistance," the agency said. "We are closely monitoring local authorities’ investigation into this brutal attack."

The latest U.S. State Department travel advisory in mid-December listed Tamaulipas state as “do not travel” due to the prevalence of crime and kidnapping.

“Heavily armed members of criminal groups often patrol areas of the state in marked and unmarked vehicles and operate with impunity particularly along the border region from Reynosa northwest to Nuevo Laredo,” the advisory said. That was where the family was driving.

Back in November, a family was attacked in a deadly ambush in Sonora. Three women and six children were killed at the hands of suspected cartel gunmen.

Fox News' David Aaro and The Associated Press contributed to this report.