One person was in custody Wednesday but many questions remained unanswered surrounding the brutal massacre that took the lives of nine family members in northern Mexico.

Monday’s slaughter was carried out by cartel gunmen who ambushed three SUVs along a dirt road in an attack that left one vehicle a burned-out, bullet-riddled hulk. Three women and six children died in the carnage.

 Eight children survived the attack in the remote, mountainous area of Sonora state. Five of them were flown by military helicopters to U.S. hospitals. Sonora state health officials said they were “stable” at the moment of transfer.

We know what happened - but why?

Leah Staddon, another relative, told The Arizona Republic that the three mothers with dual U.S. and Mexican citizenship were driving from Bavispe to a wedding in LeBaron, another Mormon-offshoot community in the state of Chihuahua, when their three SUV's loaded with children were attacked.

 The family’s vehicles were sprayed with gunfire on a road near Rancho La Mora in a remote and mountainous area where the Sinaloa cartel has been engaged in a turf war with another gang. Authorities have theorized the attackers worked for a cartel that mistook the family's SUVs for a rival gang's convoy.

How are the suspect and hostages connected to the massacre? 

Criminal investigators said late Tuesday that a suspect was arrested and wass under investigation for possible connections with the deaths. In a statement posted on Facebook, the Agency for Criminal Investigation for the state of Sonora said that the suspect was found in the town of Agua Prieta, right across from the Arizona border, holding two hostages who were gagged and tied inside a vehicle.

The suspect, whose gender was not specified in the release, had four assault rifles and ammunition, as well as various large vehicles including a bullet-proofed SUV, the agency said. One of the vehicles was connected with a robbery in Phoenix, Arizona.

Cartels in Sonora, Mexico

César Peniche, the attorney general of Chihuahua, told Univision that the region where the massacre occurred is operated by a group connected to the Sinaloa cartel called “The Jaguars.”

The group operates between Chihuahua and Sonora and their leader is Francisco Arvizu, also known as “The Jaguar,” Peniche told the Spanish language network. There is another rival group called “The Line,” which is connected to the Juárez cartel and is commanded by Roberto González Montes.

Peniche says that these two groups are constantly disputing the coming and going of drugs in the area, Univision reported.

Sonora is considered a key location by the international drug trade and human trafficking network. It is labeled as a “Level 3: Reconsider Travel” by the U.S. State Department because of the risk of crime.

It remains unknown whether the anti-crime reputation of the victims' extended family influenced the attack on Monday morning. The victims – all dual U.S.-Mexican citizens – were related to the LeBaron family, whose members have clashed with drug traffickers over the years. One of them, Benjamin LeBaron, was murdered by the cartels in 2009 after he founded neighborhood patrols against them.

Trump tweets support, but Mexico is skeptical

The massacre drew the attention of U.S. President Donald Trump, who blamed "two vicious drug cartels" for the attack.

"This is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth. We merely await a call from your great new president!" Trump tweeted on Tuesday morning.

Trump's offer to the Mexican government was met with skepticism by Mexico's President Andrés Manuel López Obrador.

During his daily press conference at his presidential palace in Mexico City, he told reporters that, despite Trump's offer, taking on the cartels was an internal security matter.

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Still, he kept the door open for some limited cooperation between his government and U.S. officials to help investigate Monday's ambush.

La Mora, LeBaron: What are these Mormon communities doingin Mexico?

The families killed in Monday’s ambush highlight the long history of fundamentalist members of The Church of Jesus Christ of Latter-day Saints who originally fled from the U.S. to Mexico to practice polygamy.

Family members said the victims were members of a fundamentalist Mormon community in the state of Sonora and had dual U.S. and Mexican citizenship.

But the practice of polygamy has mostly been abandoned in the communities in Mexico, experts say.

Mormon families from Utah began settling in Chihuahua and Sonora in the mid-1880s as the United States began placing restrictions on polygamy on The Church of Jesus Christ of Latter-day Saints.

The Mormons did not want to abandon their wives and families, so they moved to Mexico, said Gordon Bluth, an Arizona businessman who was born in one such community in Mexico and has studied the history of Mormons in the country.

Under an agreement with the Mexican government, the Mormons purchased 100,000 acres of land and eventually established eight colonias, or towns, in the states of Chihuahua and Sonora.

One of the eight colonias, Colonia LeBaron, was founded by Alma Dayer LeBaron in the 1920s. LeBaron was among the fundamentalist Mormons who moved to Mexico to evade U.S. law enforcement and continue practicing polygamy.

One of his sons, Ervil LeBaron, founded his own fundamentalist polygamist church, called the Church of the Firstborn, that later took on a cult following in the 1970s. 

The Church of the Firstborn mostly dissolved after LeBaron's death in 1981 and polygamy is no longer common in Colonia LeBaron or in other Mormon colonies, Bluth said.

The three families who were ambushed Monday were traveling from Colonia Bavispe, in Sonora where they lived, to a wedding in Colonia LeBaron in Chihuahua, said Staddon.

Although some of those killed shared the same last name of LeBaron, they belonged to a separate community called La Mora and had no ties to the Church of the Firstborn, said Cristina Rosetti, a Salt Lake City-based scholar on Mormon fundamentalists in Mexico.

Contributing: David Jackson, USA TODAY; Rafael Carranza, Daniel González and Bree Burkitt, Arizona Republic; Associated Press. Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.