Coast Guard Says It Took Fire Near Garceno, Texas. Mexico Says It Has No Evidence, and Both Countries Have Sent Troops

On Sept. 26, Coast Guard Forces Rio Grande personnel were intercepting migrants crossing the river alongside other federal agencies near Garceno, a small town in Starr County, Texas. The Coast Guard says they "encountered gunfire" from the Mexican side and returned fire.

No one was hurt. No Coast Guard equipment was damaged. The service says it is investigating with federal partners and has not said who fired, or who fired first.

That is where the confirmed facts thin out. What followed was a large, fast, two-country military buildup.

The U.S. response

In the days after the incident, the U.S. military said it was repositioning hundreds of troops and equipment into the Rio Grande Valley. A U.S. Northern Command spokesperson described the move as an effort to "rapidly reinforce U.S. forces and federal partners" under Operation Ardent Vanguard. The Pentagon's Joint Task Force-Southern Border calls the surge Operation Unified Resolve.

The task force says the mission will increase patrol capacity, add monitoring and detection capabilities, and reinforce key locations in support of DHS and Customs and Border Protection.

The task force also framed the move as planned preparation for a seasonal rise in attempted illegal activity. It cited the Sept. 26 encounter as an example, not as the sole trigger. Read that way, the encounter was one factor among several, not the single cause of the deployment.

Al Jazeera reports the force includes helicopters, drones and anti-drone equipment. Officials have not publicly confirmed a troop number or said how long the deployment will last.

The Coast Guard has been on this stretch for a year. It launched Operation River Wall in October 2025, adding personnel, boats and other assets across roughly 260 miles of the Rio Grande.

Mexico's response

Mexico sent forces of its own. About 500 Army and National Guard personnel were deployed to its side of the border. The Mexican Navy and Foreign Ministry then announced a further 159 ground troops, 11 vehicles and two drones for the Tamaulipas side.

In a joint statement, Mexican officials said the relationship with Washington rests on four pillars: "respect for sovereignty, shared responsibility, mutual trust, and cooperation without subordination." Al Jazeera reports the joint effort is called Operation Mirror.

U.S. Ambassador Ronald Johnson, a former Army Green Beret and CIA officer who has served in Mexico City since May 2025, wrote on X that the embassy is coordinating with Mexican forces "deploying to the border area where U.S. Coast Guardsmen were fired upon." He added: "Together, we intend to patrol both sides of our shared border, protect our communities, and make it more difficult for criminal and terrorist organizations to operate."

Mexico disputes the premise

Then came Sheinbaum. At her Monday news conference on Oct. 5, she said Mexico had asked Washington for its evidence. "We asked for all the evidence because we have no evidence," she said.

She added that Mexico's Army, Navy and National Guard had not detected any shots fired from Mexican territory toward the United States. She also said the Mexican deployment was designed "to forestall any issues" that might arise.

So one government says its personnel were shot at and returned fire. The other says its forces detected nothing and wants proof. The Coast Guard's own statement leaves the shooters unidentified, which means neither account has been tested in public.

Who was shooting?

Cartel involvement is widely assumed but not established. Breitbart Texas reported that gunmen from the Gulf Cartel in Miguel Alemán fired on the boats. The Coast Guard has not identified anyone, and no suspects have been named publicly.

Texas Gov. Greg Abbott declined to confirm a cartel link when asked, saying only, "That is what I've heard." Hector Garza, a vice president of the National Border Patrol Council, said, "I think we can confirm that it is a cartel," while also acknowledging the investigation was ongoing.

A spokesperson for Abbott, whose Texas Military Department works with federal forces on the border, declined to add anything.

What is at stake

The incident has produced a joint patrol arrangement, with troops on both sides of a river that has long been a smuggling corridor. The U.S. and Mexican governments both describe it as cooperation, and both have a stake in keeping it that way.

But troops on both banks of a river, with a public disagreement over whether the triggering event happened as described, is a fragile setup. A shot fired by someone in uniform, or a mistaken identification of a Mexican patrol, would create a far bigger problem than the one that started this.

The immediate question is whether the Coast Guard investigation produces anything Washington can hand to Mexico City. Sheinbaum has asked for evidence, the Coast Guard says its inquiry continues, and so far no one has publicly said who fired.