A 13-year-old survivor of the attack by suspected Mexican drug cartel gunmen on a convoy of US Mormons hid six siblings in bushes before walking 23km (14 miles) to get help, his family said.
Eight children survived Monday's attack in northern Mexico in which three women and six children were killed.
Five of the children have bullet wounds, US media report.
The victims are members of the LeBaron family, linked to a Mormon community that settled in Mexico decades ago.
Mexico's security minister said the group could have been targeted accidentally as a result of mistaken identity. However family members have said the community, known for speaking out about cartel violence, had received threats in the past.
Sonora state in northern Mexico is being fought over by two rival gangs, La Línea, which has links to the larger Juárez cartel, and "Los Chapos", which is part of the Sinaloa cartel.
Mexican investigators on Tuesday said one person had been arrested and was being investigated for possible links to the attack. The suspect was found in the border town of Agua Prieta with a haul of weapons and two gagged hostages inside a vehicle, the Associated Press reported.
How did the children escape?
A group of three mothers and their 14 children set off in three cars from the community La Mora in Sonora state on Monday morning. The women had been travelling together "for safety reasons", a relative told CNN.
Shortly after leaving, all three of their cars were at different points ambushed by gunmen near Bavispe.
Devin Langford, 13, was travelling with eight of his siblings and his mother in one vehicle. His mother, Dawna Langford, was killed along with two of his brothers in the attack.
The teenager escaped with six of his siblings and hid them in bushes. He then walked for six hours to the community's base in La Mora, relative Kendra Lee Miller wrote on Facebook.
One of Devin's sisters, nine-year-old McKenzie, then left the remaining five siblings and walked for four hours in the dark after Devin failed to return. She was later found by rescuers.
Who are the other victims?
Five of the victims - 30-year-old Rhonita Maria Miller and her eight-month-old twins Titus and Tiana, 12-year-old Howard Jr and 10-year-old Krystal - died after their car was targeted by gunmen. At some point, the vehicle caught fire and exploded.
Christina Langford Johnson, 31, was also killed in a third vehicle.
Her seven-month-old baby, Faith Langford, survived the attack. She was found on the floor of the vehicle in her baby seat.
Ms Langford Johnson reportedly got out of the vehicle with her hands raised to ask the attackers to stop shooting but was gunned down, witnesses said.
After Devin alerted the community, members armed themselves, intending to set out for the scene of shooting. But they decided to wait for reinforcements after "realising they would be risking death, since there had been continual shooting for hours, all over the mountains near La Mora", Ms Miller said.
Faith was found 11 hours after the attack by community members.
The survivors, including the children with gun injuries, were then transferred to get medical help and eventually were airlifted to the US city of Phoenix.
In a tweet President Donald Trump described the victims as a group of "wonderful family and friends" who had "got caught between two vicious drug cartels, who were shooting at each other".
What has the reaction been?
Mr Trump said he stood ready to offer support to combat the problem of cartel violence and "do the job quickly and effectively". The FBI has reportedly offered to assist Mexican authorities in the investigation.
Mexico's President, Andrés Manuel López Obrador, said Mexico would act with "independence and sovereignty" in pursuing the criminals behind the attack.
Claudia Pavlovich Arellano, governor of the state of Sonora, described the perpetrators as "monsters".
Julian LeBaron, a cousin of one of the women, demanded answers.
"We want to know exactly who was behind this, why they did it and from where they are, and we need that information to be true," he told Mexican radio. "We don't know who would attack women and children."
Who are the Colonia LeBaron?
The victims were members of a community called Colonia LeBaron which was founded by a breakaway Mormon group in the first half of the 20th Century after the Church of Jesus Christ of Latter-day Saints in the US started cracking down on polygamy.
The mainstream Mormon Church publicly rejected polygamy - the custom of having more than one spouse at the same time - in 1890 and after that some groups who wished to continue the practice broke away.
The Colonia LeBaron community now includes both Mormons and Catholics who have settled there. Members are known for standing up to local drug gangs and speaking out about the high levels of cartel violence. It has about 3,000 members, some of whom practise polygamy.
While local media say the convoy of cars may have been mistaken for that of a rival gang, the LeBaron community has been targeted by the cartels in the past. In 2009, Erick LeBaron was kidnapped for ransom. The community took a stand and said it would not pay for his release as that would just encourage future kidnappings.
Erick LeBaron was eventually released without a ransom being paid. But months later, his brother Benjamin was beaten to death. Benjamin's brother-in-law was also killed.
In 2010, Julian LeBaron published an article in the Dallas Morning News calling for Mexicans to stand up against organised crime.
Mr LeBaron also told Mexican radio on Tuesday that his family had received threats. "We reported the threats, and these are the consequences," he said.
Last year, the family clashed with local farmers who accused the LeBarons of using excessive amounts of water to grow walnut trees on their land, allegedly leaving nearby farms dry.
The Colonia LeBaron community has in the past demanded to be allowed to create its own security force.
How bad is drug-related violence in Mexico?
The power and influence of the Sinaloa cartel was on display last month when its members barricaded streets and clashed with security forces in Culiacán after one of their leaders and the son of jailed drug kingpin Joaquín "El Chapo" Guzmán was arrested.
With the security forces outnumbered and surrounded, the Mexican government took the controversial decision to free Ovidio Guzmán López to prevent further bloodshed.
The BBC's Will Grant in Mexico says pressure is growing on the government to adopt more coherent security strategies following this brutal attack on families.