The Mexican police officers fired off rounds as U.S. Border Patrol agents walked into Smuggler’s Gulch, a ravine a couple of miles east of the downtown port of entry in Nogales.

The shots hit one agent, injuring him severely, and set off a round of international recriminations.

U.S. officials said the Mexican police did it on purpose. The Mexican government said officers were shooting at robbery suspects in the gulch, not at the agents.

It sounds like news from last month, but it happened 19 years ago, in August 1995. And even then, it wasn’t the first “border incursion,” just the latest and most severe of that time.

These occasional border-crossing incidents — like shots fired from a helicopter June 26 south of Sells and an armed encounter in January near Sasabe — have been a longstanding feature of policing the border.

In June, U.S. Rep. Duncan Hunter of California got a response to a letter he had sent U.S. Customs and Border Protection about incursions. The upshot: There have been 300 known incidents in which Mexican police or soldiers crossed the border since Jan. 1, 2004 — a rate of 30 per year.

That strikes me as a lot. True, most are resolved with relative calm. But we need to find a way to apply some accountability to these incidents — transparency in every case and consequences where necessary.

“Can you imagine if a Border Patrol agent raised a gun on a Mexican cop on Mexican soil?” asked Sylvia Longmire, a Tucsonan whose book, “Border Insecurity: Why Big Money, Fences and Drones Aren’t Making us Safer,” came out this year. “I don’t think there’s an excuse. I don’t think an apology cuts it.”

We have had infrequent experiences with U.S. agents crossing the line, though you’ve got to think it happens more often than we know. In 1997 an agent followed a suspect into Agua Prieta, Sonora, and was lucky to make it back unharmed. The same year another agent drove about 15 feet into Nogales, Sonora, to drop off illegal immigrants, including a woman who was injured.

The incidents were big stories and so were the outcomes: Both agents were fired.

In more recent years, U.S. agents have fired across the line several times, shooting people they said were throwing rocks at agents. The Border Patrol hasn’t been a paragon of transparency in dealing with those cases, so it’s unclear if the agents have been held accountable.

But our system allows for victims to hold the agency accountable in civil courts. Last week, the 5th U.S. Circuit Court of Appeals ruled that the family of a Mexican teen shot to death by a Border Patrol agent in El Paso can sue even though the family is not American and he was shot on Mexican soil.

When Mexican officers cross the line, Mexico usually gives one of two explanations: They didn’t mean to, or they didn’t do it all.

The January incident was a pretty typical example of the former: Two Mexican soldiers and two Border Patrol agents came across each other in the brush west of Sasabe, 50 yards north of the border. Both drew weapons. After tense moments, they talked and realized the Mexicans had wandered north of the line. The agents took the soldiers’ names and directed them back across the border.

The June 26 incident, an example of the latter explanation, is more concerning. Mexican soldiers and police conducted an operation to seize a ranch used by smugglers, just south of the international line on the Tohono O’odham Nation. U.S. officials had advance knowledge of the operation, but whether they participated is unclear.

Here’s how Customs and Border Protection explained the incident: “At approximately 5:45 a.m. Thursday morning, a Mexican law enforcement helicopter crossed approximately 100 yards north into Arizona nearly 8 miles southwest of the Village of San Miguel on the Tohono O’odham Indian Nation while on a law enforcement operation near the border. Two shots were fired from the helicopter but no injuries or damage to U.S. property were reported.”

Mexican officials denied the chopper crossed the border or fired at agents.

“With the seizure of the ‘La Sierrita’ ranch, the flow of a large quantity of migrants and drugs crossing from Mexico to the United States has been stopped. These actions by the Mexican government reaffirm our commitment to combating organized crime in a coordinated manner between different government agencies to achieve a Mexico in peace.”

FBI spokesman Perryn Collier said the agency is investigating: “We need to figure out what happened. It’s difficult because you have one party saying it happened this way, you have another party saying it happened another way.”

The FBI probe is a good step: At least someone is working to establish the facts.

Those who have worked border crime point not toward accidents but toward corruption as a principal reason for the incursions. When Mexican soldiers or officers cross the line, they may be guiding a drug load or creating a diversion to distract agents from where the load is crossing.

Tony Coulson, who led the Drug Enforcement Administration’s Tucson office until his retirement in 2010, said his agents operated under the assumption that Mexican officers were corrupt, except in the case of a few vetted Mexican marine units.

Pima County Sheriff Clarence Dupnik, who spent decades on anti-border-crime efforts, pointed to another complicating factor: It can be hard to tell who’s a real Mexican soldier, who’s a trafficker in fatigues, and where anyone’s allegiances lie.

Even more frustrating, the State Department and higher-ups in the Department of Homeland Security often seem to place a higher priority on smoothing over differences than on holding people accountable. To the State Department, it seems, a strongly worded diplomatic note is enough accountability.

There is reason to consider the international relationship in deciding how to react. Binational cooperation is at a high point, said Christopher Wilson, a border expert at the Woodrow Wilson Center’s Mexico Institute in Washington, D.C.

“We historically did have a relationship of mutual recrimination, but we have been able to move beyond that,” he said. “If we let the relationship blow up every time mistakes were made or corruption affected U.S. law enforcement, we wouldn’t have a relationship.”

What the U.S. government hasn’t found is a level of accountability for the individual Mexican soldiers and officers involved that goes beyond a diplomatic note but doesn’t unnecessarily ruin the relationship. Investigating the incursions, revealing the results and pursuing charges or other consequences where warranted would be a great start.

Contact columnist Tim Steller at or 807-7789. On Twitter: @senyorreporter