LA UNIÓN, Mexico -- Gunmen believed to be linked to drug traffickers shot a pregnant American consulate worker and her husband to death in the violence-racked border town of Ciudad Juárez over the weekend, leaving their baby wailing in the back seat of their car, the authorities said Sunday. The gunmen also killed the husband of another consular employee and wounded his two young children.
The shootings took place minutes apart and appeared to be the first deadly attacks on American officials and their families by Mexico's powerful drug organizations, provoking an angry reaction from the White House. They came during a particularly bloody weekend when nearly 50 people were killed nationwide in drug-gang violence, including attacks in Acapulco as American college students began arriving for spring break.
The killings followed threats against American diplomats along the Mexican border and complaints from consulate workers that drug-related violence was growing untenable, American officials said. Even before the shootings, the State Department had quietly made the decision to allow consulate workers to evacuate their families across the border to the United States.
In Washington, President Obama denounced the "brutal murders" and vowed to "work tirelessly" with Mexican law enforcement officials to prosecute the killers. Secretary of State Hillary Rodham Clinton said the killings underscored the need to work with the Mexican government "to cripple the influence of trafficking organizations at work in Mexico."
In a sign of the potential international reverberations of these killings, President Felipe Calderón of Mexico similarly expressed his indignation and condolences and said he would press forward with "all available resources" to control the lawlessness in Ciudad Juárez and the rest of the country.
The F.B.I. was sending agents to Ciudad Juárez on Sunday to assist with the investigation and American diplomats were en route to meet with their Mexican counterparts, said Roberta S. Jacobson, the American deputy assistant secretary of state who handles Mexico.
"We take very seriously when our employees are harmed, whether the intention was to harm U.S. employees or not," she said in a telephone interview. "The question of whether this represents some ratcheting up of the drug war will depend on the reason behind the killings."
The coordinated nature of the attacks, the automatic weapons used and the location in a city where drug cartels control virtually all illicit activity point toward traffickers as the suspects, said Mexican and American officials, declining to be identified. Officials with the state of Chihuahua issued a statement Sunday night saying that initial evidence, corroborated by intelligence from the United States, pointed to a gang known as Los Aztecas, which is linked to the major drug cartel in Ciudad Juárez.
American interests in Mexico have been attacked by drug traffickers before but never with such brutality. Attackers linked to the Gulf Cartel shot at and hurled a grenade, which did not explode, at the American consulate in Monterrey in 2008.
The shootings in Ciudad Juárez took place in broad daylight on Saturday as the victims were en route home from a social gathering at another consulate worker's home. The first attack was reported at 2:32 p.m.
Jorge Alberto Salcido Ceniceros, 37, the husband of a consular worker, was found dead in a white Honda Pilot, with bullet wounds to his body, the authorities said. In the back seat were two wounded children, one aged 4 and one 7. They were taken to the hospital.
Shell casings from a variety of caliber weapons were found at the scene.
Another call came in 10 minutes later, several miles away. This time it was a Toyota RAV4 with Texas plates that had been shot up, with two dead adults inside and a baby crying from a car seat in the back. Mexican officials identified the couple as Lesley A. Enriquez, 25, a consulate employee, and her husband, Arthur H. Redelf, 30, from across the border in El Paso, where he worked at the county jail.
Ms. Enriquez, an American citizen, was shot in the head. Her husband was shot in the neck and left arm. A 9-millimeter bullet casing was found at the scene.
Cmdr. Gomecindo López of the El Paso County Sheriff's Department, who is acting as a spokesman for the family, said Ms. Enriquez had been pregnant.
In his statement, Mr. Obama was quick to laud the antidrug offense begun three years ago by Mr. Calderón, which is backed by more than $1 billion in United States money. But a growing chorus of critics of Mexico's drug war, which has led to spiraling levels of violence in hot spots across the country, has asked Mr. Calderón to find a new approach.
One critic, former Foreign Minister Jorge Castañeda, said in a telephone interview on Sunday that given the violence "it is surprising that this has not happened before." The killings, he said, ought to prompt the Obama administration to rethink its support for what he called Mr. Calderón's failed strategy.
In fact, Mr. Calderón is scheduled on Tuesday to make his third visit to Ciudad Juárez in the last five weeks as he tries to contain the disastrous public relations fallout from the killing of 16 people in January that Mr. Calderón first brushed off as "a settling of accounts" between members of criminal gangs.
It turns out the victims of the massacre were mostly students celebrating a birthday. By all accounts, they were just young people from a rough neighborhood trying to steer clear of the drug gang violence that has turned Ciudad Juárez into Mexico's deadliest city. More than 2,000 people were killed there last year, giving it one of the highest murder rates in the world.
Those killings and Mr. Calderón's blunder -- he was in Japan at the time and later blamed mistaken information for his error -- prompted the government to shift course after three years of its military-led crackdown on drug cartels and acknowledge that it has to involve citizens in the fight and deal with the social breakdown fueling the violence.
As killings have multiplied in Mexico, the government has long argued that the overwhelming majority of the casualties of the drug war are involved in the narcotics business. "The argument is absurd that the killings are a sign of his success," Mr. Castañeda said, repeating an oft-heard refrain of both the Mexican and American governments.
Concerned about the rising violence, the State Department had decided that employees at a string of consular offices along the Mexican border -- Tijuana, Nogales, Ciudad Juárez, Nuevo Laredo, Monterrey and Matamoros -- could temporarily evacuate their families to the United States. That decision was not formally announced until Sunday.
Marc Lacey reported from La Unión, Mexico, and Ginger Thompson from Washington. Helene Cooper contributed reporting from Washington, and Elisabeth Malkin and Antonio Betancourt from Mexico City.
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