MEXICO CITY (AP) - Drug cartel gunmen ambushed three SUVs along a dirt road, slaughtering at least six children and three women - all of them U.S. citizens living in northern Mexico - in a grisly attack that left one vehicle a burned-out, bullet-riddled hulk, authorities said Tuesday.

The dead included 8-month-old twins. Eight children were found alive after escaping from the vehicles and hiding in the brush, but at least five had bullet wounds or other injuries and were taken to Phoenix for treatment.

The gunmen apparently killed one woman, Christina Langford Johnson, after she jumped out of her vehicle and waved her hands to show she wasn't a threat, according to an account published by family members and corroborated by prosecutors and a relative in a telephone interview.

Around the running ambush scene, which stretched for miles, investigators found over 200 spent shell casings, mostly from assault rifles.

Mexican Security Secretary Alfonso Durazo said the attackers may have mistaken the group's large SUVs for those of rival gangs. The attack took place in a remote, mountainous area where the Sinaloa cartel has been engaged in a turf war with another gang.

All of the victims were believed to be members of the extended LeBaron family, who live in a decades-old settlement founded by an offshoot of The Church of Jesus Christ of Latter-day Saints and have run afoul of the drug traffickers over the years. A LeBaron was killed a decade ago after denouncing the cartels.

"There's apparently a war right now," a relative who did not want his name used for fear of reprisals said wearily. "It's been going on for too long."

In a tweet, President Donald Trump immediately offered to help Mexico "wage WAR on the drug cartels and wipe them off the face of the earth." But Mexican President Andrés Manuel López Obrador rejected that approach, saying his predecessors waged war, "and it didn't work."

The victims lived in the hamlet of La Mora in Sonora state, about 70 miles (110 kilometers) south of Douglas, Arizona. A number of extended families from LDS breakaway groups live in farming communities clustered around the Chihuahua-Sonora state border.

Many members were born in Mexico and thus have dual citizenship. While some of the splinter groups were once polygamous, many no longer are.

State prosecutors said Johnson was found 15 yards (meters) away from her Suburban van, shot to death. Her 7-month-old daughter, Faith Marie Johnson, was discovered uninjured in her car seat in the SUV.

Kendra Miller, a relative, wrote that the baby's car seat "seemed to be put on the floor, by her mother to try and protect her. ... She gave her life to try and save the rest."

A short distance away, Dawna Ray Langford, 43, lay dead in the front seat of another Suburban, along with the bullet-riddled bodies of her sons, ages 11 and 2.

Some of the children who escaped had grisly wounds. One had been shot in the face, another in the foot. One girl suffered gunshot wounds to her back and foot.

Cowering in the brush, one boy hid the other children and then walked back to La Mora to get help. Another girl, who was initially listed as missing, walked off in another direction, despite her gunshot wounds, to get help.

A group of male relatives set out to try to rescue the youngsters but turned back when they heard gunfire ahead.

The relative who did not want his name used said in an interview that when they finally made it to the scene where the ambush started - about 11 miles (18 kilometers) from where the two other mothers were killed - they found a burned-out, shot-up Chevy Tahoe.

Inside, they saw they charred remains of Rhonita Miller, 30, her 10-year-old daughter, a son, 12, and 8-month-old twins. They were "burnt to a crisp," the relative said.

The gunmen had riddled the car with dozens of bullets and apparently hit the gas tank, causing it to explode. There was nothing the relatives could do but watch the still-smoldering vehicle.

"When we were there, the cartels from Sonora, there were probably 50 or 60 of them, armed to the teeth, about a mile on this side," said the relative.

A member of the extended LeBaron family, Benjamin LeBaron, an anti-crime activist who founded neighborhood patrols against cartels, was killed in 2009 along with a neighbor.

"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 young children, and some missing," Trump wrote.

He tweeted that the U.S. "stands ready, willing & able to get involved and do the job quickly and effectively," adding: "The great new President of Mexico has made this a big issue, but the cartels have become so large and powerful that you sometimes need an army to defeat an army!"

But Mexico's president said: "The worst thing you can have is war."

It was the second failure in recent weeks for López Obrador's "hugs not bullets" anti-crime strategy. Two weeks ago, Mexican forces seized a son of imprisoned drug lord Joaquin "El Chapo" Guzman but had to release him after cartel henchmen launched a furious counterattack in Culiacan, Sinaloa.

A suspect was detained near Agua Prieta, the Sonora prosecutor's office said, but it was unclear whether the person had taken part in the ambush. The suspect had assault rifles and a .50-caliber sniper rifle and was holding two bound kidnap victims, authorities said.