Nine Americans dead, including six children, and 13 more missing — and it all might be a case of mistaken identity. An ambush on a highway in Mexico between warring drug cartels appear to have mistakenly targeted a convoy of Mormons traveling in SUVs at night. Among the dead are eight-month-old twins and their mother:

At least nine U.S. citizens — including six children — were killed in what local media described as a highway ambush in the Mexican border state of Sonora late Monday, a family member told NBC News.

The dead included 8-month-old twins, said Kendra Lee Miller, who is related to many of the victims. Some of the eight survivors — all children — sustained serious injuries. …

Earlier another relative of one of the victims, Willie Jessop, told NBC News on the phone from Utah that a number of people were traveling in a motorcade consisting of several families when they came under the attack.

Jessop said three of the cars were shot at and one of them was set on fire based on the information he has been receiving from other family members at the scene.

He added that they have been trying to mobilize Mexican federal officials and have been in contact with the FBI.

“Everyone is in so much shock,” he said. “It’s just unbelievable and there’s just no way to comprehend it.”

Three American families had wanted to attend a wedding in Mexico, and had been traveling in a caravan to get there — presumably for safety. It’s not clear exactly why the drug cartels made this mistake, but some more sensational reports suggest that it didn’t much matter to them when they found out they were wrong. Bear in mind that The Sun routinely runs with fuzzy details that turn out to be unsupported, but if this is true, hoo boy:

In disturbing scenes, gunmen fired at one child running away before torching a car as victims burned to death inside it.

One mother was shot in the chest as she raised her hands to surrender, while other terrified children managed to escape and hide by the roadside, according to reports.

A nine-year-old girl also survived after being shot in the back as she ran away from the gunmen, it’s claimed.

That’s as cowardly and brutal as it gets, not even counting the attackers’ decision to burn at least one of the vehicles in the aftermath. That kind of thuggish and indiscriminate brutality has Arizona on edge. The state has issued a travel advisory, and border towns report hearing gunfire across the border:

The drug cartels have begun attempting to impose their will by force northern Mexico. The Sinaloa cartel occupied Culiacán after government forces arrested the son of Joaquín “El Chapo” Guzmán, forcing city leaders to order his release from local military forces, after threatening to kill every single person in the city. That has driven a political wedge between President Andrés Manuel López Obrador and the military at a time when political unity is most critical.

The massacre of nine Americans — and perhaps more — might drive another wedge between the US and Mexico. Donald Trump might be inclined to use this as an argument that US troops should be in Mexico dealing with the cartels rather than in Syria dealing with a Sunni-Shi’a war that goes back more than a millennium, or at least on the border to make sure the cartel war doesn’t spill into the US. In the short term, a retaliatory strike against the cartels by the administration might not be too hard to imagine, even if it might end up making matters more complicated regarding Mexico’s cooperation on immigration enforcement. The next steps after this outrage and atrocity are rather murky in the first hours.

What is clear is that Mexico is a mess, and that López Obrador has been unable to exert any impact on the cartels. At some point, that will become a US problem whether we want it or not. And this horror might push that date much closer to the present.

Update: And just after I wrote that, Donald Trump weighed in on the events. He’s standing by for a call from López Obrador:

How long Trump will wait for an invitation before deciding to assume he has one?