A suspect was arrested near the Arizona border with Mexico in connection with the deaths of nine U.S. citizens - six children and three women – Monday who were living in a Mormon community about 70 miles south of Douglas, Ariz., investigators said early Wednesday.

The victims’ convoy came under fire during the day in an ambush by gunmen believed to be affiliated with a drug cartel in Mexico.

MEXICAN CARTEL MASSACRE: 9 AMERICANS, INCLUDING 6 CHILDREN, FROM MORMON OFFSHOOT MURDERED

MEXICAN DRUG CARTEL MASSACRE VICTIMS WERE KIN TO ANTI-CRIME ACTIVIST KILLED 10 YEARS AGO

The Agency for Criminal Investigation said in a statement on Facebook the suspect was found in the town of Agua Prieta, right across the border from Douglas, Arizona. The suspect was holding two hostages who were bound and gagged inside a vehicle.

Investigators found four assault rifles and a bulletproof SUV.

Officials have said that the gunmen may have mistaken the group's large SUVs for those of a rival gang amid a vicious turf war.

Eight young children - including babies - survived the attack by hiding in the brush and even though they were wounded some walked miles to get help. Five badly wounded children were transported to hospitals in Arizona for treatment.

BABY FOUND UNHARMED IN BULLET-RIDDLED VEHICLE; BOY, 13, HID SIBLINGS IN BUSHES

A relative of 13-year-old Devin Blake Langford, who was uninjured in the attack, said he took charge of the group and ended up walking 14 miles for help.

"After witnessing his mother and brothers being shot dead, Devin hid his six other siblings in the bushes and covered them with branches to keep them safe while he went for help," she said. "When he took too long to return, his 9-year-old sister left the remaining five to try again."

His sister, Mckenzie Rayne Langford, was eventually rescued.

US VICTIMS OF MEXICAN CARTEL MASSACRE RANGE FROM 8-MONTH-OLD TWINS TO 43-YEAR-OLD MOTHER

Relatives tried to reach the children but were prevented by gunfire.

One mother reportedly hid her baby inside her car before she got out with her arms raised and was killed by the cartel.

"This sort of thing shouldn't go unnoticed," Austin Cloes, a relative of one of the victims, said. "And these sorts of people shouldn't just be buried without their names being put out there. These are great people."

The FBI meanwhile has offered assistance to the Mexican government, hours after President Andres Manuel Lopez Obrador rejected President Trump's overture to "wage war" on the country's drug cartels in response to the brutal slayings.

“If Mexico needs or requests help in cleaning out these monsters, the United States stands ready, willing & able to get involved and do the job quickly and effectively,” Trump tweeted Tuesday. “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!”

Obrador thanked Trump but declined the help, saying, "The worst thing you can have is war."

CLICK HERE TO GET THE FOX NEWS APP

"We declared war, and it didn't work," Lopez Obrador said, referring to the policies of previous administrations. "That is not an option."

The Associated Press contributed to this report