MEXICO CITY -- An alleged Zetas drug cartel member arrested in the killing of a U.S. immigration agent told soldiers Wednesday the attack was a mistake, saying gunmen mistook the officer's SUV for a vehicle used by a rival gang, the army said.
Julian Zapata Espinoza -- known by the nickname "El Piolin," or Tweety Bird, apparently because of his short stature -- was captured along with five other suspected Zetas members during an army raid Wednesday on gang safehouses in the northern city of San Luis Potosi.
President Barack Obama and other top U.S. officials offered congratulations for the arrests a week after the killing.
Attorney General's Office spokesman Ricardo Najera told The Associated Press that Zapata Espinoza had been arrested on unspecified federal charges in 2009, but jumped bail and disappeared until he was re-arrested Wednesday.
U.S. Immigration and Customs Enforcement agent Jaime Zapata was shot to death and fellow agent Victor Avila was wounded near that city Feb. 15 when they were attacked while driving on a highway.
"That event occurred because of the characteristics of the vehicle, given that they (the suspects) thought it was being used by members of a rival criminal group," an army spokesman, Col. Ricardo Trevilla, said.
The two agents were in a Chevrolet Suburban. Mexico's drug cartels frequently set up roadblocks and ambushes to steal large SUVs and pickups, vehicles they like to use.
Zapata and Avila, who worked at the U.S. Embassy, were attacked as they returned to Mexico City from a meeting with other U.S. personnel in the state of San Luis Potosi. Avila was shot twice in the leg and is recovering in the United States.
Some reports said the two were stopped at a roadblock, while others said they were run off the road by other vehicles. The Mexican government does not authorize U.S. law enforcement personnel to carry weapons.
Last week, some U.S. officials maintained the attack was an intentional ambush of the agents and said the gunmen made comments before they fired indicating they knew who their targets were.
It would not be the first time that a politically sensitive killing in Mexico was identified as a case of mistaken identity.
In 1993, gunmen linked to the Arellano Felix drug cartel killed Roman Catholic Cardinal Juan Jesus Posadas Ocampo at an airport in the western city of Guadalajara. Prosecutors later said the gunmen mistook the cardinal's luxury car for their intended target, drug lord Joaquin "El Chapo Guzman."
Several other recent high-profile cartel killings of people not involved in the drug trade, including the September killing of American tourist David Hartley, have been ascribed by law enforcement officials to cases of mistaken identity.
Though Mexico is seeing record rates of violence, it is rare for U.S. officials to be attacked. The U.S. government, however, has become increasingly concerned about the safety of its employees in the country.
In March, a U.S. employee of the American consulate in Ciudad Juarez, her husband and a Mexican tied to the consulate were killed when drug gang members fired on their cars after they left a children's party in the city across from El Paso, Texas.
Trevilla, the army spokesman, said military intelligence officers had identified Zapata Espinoza as the head of a cell of Zetas gang members in San Luis Potosi since early December, when raids in the area turned up other alleged gang members. Trevilla said Zapata Espinoza headed the Zetas' operations in the area, but did not specify what they were.
Zapata Espinoza and the five others, including a Honduran citizen, arrested Wednesday were presented to journalists Wednesday night. The army quoted Zapata Espinoza as saying two of the five had participated in the attack on the ICE agents, but did not specify which of the five.
One of the men had a swollen, bruised face. Soldiers found three women and one child and five rifles at the four houses raided, authorities said.
San Luis Potosi is at the center of a power struggle between two rival drug gangs, the Zetas and the Gulf cartel. It is also on the route north used by migrants seeking to reach the United States, and officials say cartels have begun recruiting some migrants to work for the gangs.
The White House said in a statement that the U.S. president Obama spoke with Mexican President Felipe Calderon on Wednesday and "thanked him for Mexican efforts to bring to justice the murderers."
"The president said neither the United States nor Mexico could tolerate violence against those who serve and protect our citizens, as Special Agent Zapata did so selflessly through his own life," according to the statement.
The arrest came as Calderon announced a visit to Washington to meet with Obama next week.
U.S. Homeland Security Secretary Janet Napolitano also welcomed the arrest. She said the United States "will continue to assist the ongoing Mexican investigation with every resource at our disposal and to ensure that all those responsible for Special Agent Zapata's murder face justice."
"We will also continue our vigorous and coordinated efforts to defeat the criminal organizations operating in Mexico that seek to exploit our shared border," she added in a statement.
ICE Director John Morton said in a statement that "we are encouraged by this action and appreciate the efforts by Mexico to bring Special Agent Zapata's killers to justice."