Is Mexico’s drug war spilling into the United States? Two recent cases bring new prominence — and new confusion — to this old question.

The two new cases of spillover violence, on October 30 and November 24, took place in Texas, more than 300 miles apart. Both produced murky and conflicting reports. Each involved a different Mexican crime cartel, on different kinds of missions. These probes by foreign criminals onto U.S. soil were apparently unrelated, and only coincidentally close in time.

But there is still the deeper riddle. Could the incidents be predictors of thing to come? Do they foreshadow a general tendency to bring violence north across the border?

For decades Mexican drug smugglers have had marketing links inside the United States, but the large cartels have kept most of their fighting in Mexico. There has been the unwritten rule: antagonizing U.S. law enforcement isn’t worth the risk. But this is only a custom, and customs can change. The drug war itself might be defined as a gradual breakdown of norms and inhibitions. The two recent incidents ask once again: How far will the cartels go?

The first case, which took place on October 30, north of Edinburg, Texas, was labeled as a milestone by a skeptic on spillover violence. Hidalgo County Sheriff Lupe Treviño has long urged moderation in this tricky debate, reminding everyone that crime in his border county is mostly homegrown, coming from U.S.-side perpetrators, not from a phantom invasion out of Mexico.·

But the October 30 case — in which Treviño’s deputy Hugo Rodriguez was wounded — was a milestone, according to the sheriff: a clear case of Mexican organized crime on a violent cross-border mission.

The clash involved three groups: 1) local street-gang operators working in rural Hidalgo County, 2) cartel muscle coming from Mexico to strike at the street gang, and 3) Sheriff’s Department responders reportedly drawn into the fray by a cryptic call for help. Such confusing three-way battles have long been standard in Mexico.

On October 30, a pickup containing at least four hitmen from Mexico was sent across the Rio Grande bridge and traveled 20 miles into the United States. The truck came from the Gulf Cartel, a badly battered remnant organization, holding on to influence in a 150-mile urbanized strip of borderland in Mexico, facing Texas. As the Gulf Cartel has melted down — in battles with the rival Zetas, with the Mexican government and among its own factions — a load of marijuana reportedly fell into renegade hands, and crept across the border as a freelance operation. The cartel hierarchy wanted the pot back, and, reportedly, they ignored their traditional caution to go after it, sending a squad into the U.S. to do battle for the goods.

The hit squad soon targeted a mobile home in rural Hidalgo County, where parts of the disputed load were allegedly being peddled by a Texas street gang called the Partido Revolucionario Mexicano (the political-sounding name originated in a Texas prison). Three of the mobile home entrepreneurs were taken prisoner, but before the cartel abductors could get very far with them, one escaped and called the sheriff’s department. Mysteries multiplied. The kidnappers’ pickup truck was somehow identified by arriving sheriff’s deputies and there was a traffic stop. Two of the captives reportedly were being held in the cab — which must have been crowded. As a deputy walked up, the head gunman, Daniel Gonzalez Perez, 19, reportedly opened fire, then was killed in the ensuing firefight.

This was when Deputy Rodriguez was hit by three slugs, though his armored vest stopped two, leaving only a third to draw blood, in a wound that was variously described by official statements as being in the stomach or in the thigh. At least six persons, including one woman, Salma Arellano, were arrested and charged with various crimes — raising more questions. The gunman Gonzalez was the only fatality, but a murder charge was brought against one of his apparent kidnap victims, under Texas’s “law of parties.” Official narratives had Perez exchanging fire only with deputies. This, too, sounds like the confusing battles in Mexico.

The questions would linger — as the second case arrived.

Not quite a month later, on November 21, a semitrailer was rumbling into northwest Harris County at the fringe of metro Houston, a long six hours north of the border. The big rig was carrying a hidden marijuana load, but that wasn’t all. This was a decoy operation run by undercover law enforcement, designed to flush out those waiting to receive the pot. The truck was bird-dogged by lawmen in disguised vehicles. Then suddenly three other vehicles swooped in, apparently having followed this singular parade still more secretly from the border. The new vehicles opened fire, strafing the truck and killing its driver, Lawrence Chapa, an undercover informant.

Again there was a firefight. Again a sheriff’s deputy was wounded, this time in the leg, apparently as another officer fired in the confusion. Again, one of the attacking gunmen was killed. Four more were arrested. Confessions said they were operatives of the Zetas Cartel in Mexico. Three were reportedly Mexican citizens.

Theories arose. Only 300 pounds of marijuana was in the truck, a small load to try and rip off at such a risk. The truck was not attacked on a lonely road in the countryside but in more difficult urban terrain. Some theorists said the Zetas were sending a message, that this was not an attempt to rip off a drug load but a pinpoint assassination of an informant, performed inside a U.S. city to show the Zetas’ reach. Famed as the most violent Mexican cartel, the Zetas are known for sending terrorist-style messages via bursts of violence that are never overtly explained.

Both these cases suggest that if the drug war does spill onto U.S. soil, the smoke of battle may hide much of the field.

The map above suggests why law enforcement officials are nervous in South Texas. Spillover from Mexico’s violence has been happening there for some time.

Typically, the U.S.-side arrests of drug bosses (green letters on the map) have occurred not as cartels tried to conquer U.S. territory, but as they used U.S. border areas as safe havens, escaping Mexico when feuds closed in. This occurred in 2010 with some escaping members of the Zetas, and again in 2011 with the Gulf Cartel as it was rocked by infighting. Some of the sanctuary-seekers became well established before they were caught (B, C and D on the map), some were caught almost immediately (A, E, F) and one (G) turned himself in to U.S. authorities at a border bridge, the day after his battle group was smashed in Mexico 10 miles away. Escapees in hiding can bring extra problems, as their Mexican foes cross to the U.S. and shoot at them (red numbers on the map).

Will such isolated dots connect in the future, to trace out a crisis? The answer is a matter of passionate opinion — and intense debate.

See Gary Moore’s blog.