The killings last month in the Mexican border town of Ciudad Juarez of two U.S. citizens, including an employee at the city's U.S. Consulate, along with the slaying of an Arizona rancher, have fueled concerns among U.S. officials that Americans are becoming fair game for Mexican drug gangs seeking control of smuggling routes into the United States.
For more than two years, U.S. intelligence and law enforcement officials have been warning that the dramatic rise in violence along the southwestern border could eventually target U.S. citizens and spread into this country. The violence posed what the officials called a "serious threat" to law enforcement officers, first responders and residents along the 1,951-mile border.
The numbers bear out those concerns, according to the State Department: 79 U.S. citizens were killed last year in Mexico, up from 35 in 2007. In Juarez, just across the Rio Grande from El Paso, Texas, 23 Americans were killed in 2009, compared with two in 2007.
In response, Arizona Gov. Jan Brewer and Sen. John McCain, both Republicans, have called on the Department of Homeland Security to deploy the National Guard along the Arizona border. Mrs. Brewer said the rising violence showed the "abject failure of the U.S. Congress and President Obama to adequately provide public safety along our national border with Mexico."
Rep. Gabrielle Giffords, Arizona Democrat, whose district includes the area where rancher Robert Krentz was killed, said if the slaying was connected to smugglers or drug cartels, the federal government should consider all options, including sending more Border Patrol agents to the area and deploying the National Guard.
Former Rep. Tom Tancredo, Colorado Republican, and former Rep. J.D. Hayworth, a Republican who is seeking Mr. McCain's senatorial seat, joined in the call for National Guard troops to be stationed along the border.
Mr. Hayworth said the federal government should "act now and step up its efforts to secure our borders."
Texas Gov. Rick Perry also has put into play a "spillover violence contingency plan" to address attacks on American citizens in Mexico. The plan increases border surveillance; intelligence sharing; and ground, air and maritime patrols.
A day before the March 13 Juarez killings, Mr. Perry unsuccessfully sought help from Homeland Security Secretary Janet Napolitano to use unmanned Predator drone aircraft and 1,000 additional soldiers for missions on the Mexican border. He said there was a disparity in the amount of federal resources allotted to Texas for border security.
The White House said Mr. Obama was "deeply saddened and outraged" by the killings and had pledged to "continue to work with Mexican President Felipe Calderon and his government to break the power of the drug-trafficking organizations that operate in Mexico and far too often target and kill the innocent."
The latest victims were Lesley Enriquez, 25, who worked at the U.S. Consulate in Juarez, and her husband, Arthur Redelf, 30, both U.S. citizens. They were killed March 13 when Mexican drug gang members fired shots at their sport utility vehicle as they left a birthday party.
Mr. Redelf was a 10-year veteran of the El Paso County Sheriff's Office. Ms. Enriquez was four months pregnant with their second child. The couple's 7-month-old daughter was found unharmed in the back seat.
That same day, Jorge Alberto Salcido, 37, a Mexican citizen whose wife also was an employee at the U.S. Consulate in Juarez, was killed when cartel members shot at his car at a separate location, also wounding his two young children. They had attended the same birthday party.
Mr. Krentz, 58, a longtime Douglas, Ariz., rancher, was killed Saturday. He was found by a Cochise County Sheriff's Department helicopter, slumped over his Polaris all-terrain vehicle on his 34,000-acre ranch. His dog also was shot and was critically wounded. The animal was euthanized on Sunday.
Arizona authorities said they think Mr. Krentz was shot by an illegal immigrant. Police dogs followed the tracks of the suspected killer back into Mexico, about 20 miles south. Authorities think the shooter was either a drug cartel scout or a member of a known gang of border thieves that has terrorized the area's remote ranches.
The Krentz ranch sits in an area that has become a lucrative smuggling route for Mexican drug cartels.
"It's a big deal. It's something that could be a turning point here," said Cochise County Sheriff's Office spokeswoman Carol Capas. "People in the area are on heightened alert. They're grief-stricken, saddened, and they're extremely angry."
Two years ago, U.S. Immigration and Customs Enforcement, the investigative arm of the Department of Homeland Security, said in a report that border gangs were becoming increasingly ruthless and had begun targeting rivals and federal, state and local police. ICE said the violence had risen dramatically as part of "an unprecedented surge."
Last year, the Justice Department identified more than 200 U.S. cities in which Mexican drug cartels "maintain drug distribution networks or supply drugs to distributors" - up from 100 three years earlier.
The department's National Drug Intelligence Center, in its 2010 drug threat assessment report, described the cartels as "the single greatest drug trafficking threat to the United States." It said Mexican gangs had established operations in every area of the United States and were expanding into more rural and suburban areas.
The report noted that adding to the violence were assaults against U.S. law enforcement officers assigned to posts along the southwestern border. It said assaults against Border Patrol agents increased 46 percent from 752 incidents in fiscal 2007 to 1,097 incidents in fiscal 2008 - including the January 2008 killing of an agent by the automobile of a fleeing drug suspect and the fatal shooting of another agent in July 2009.
Although no arrests have been made in the Krentz killing, there has been an arrest in the Ciudad Juarez killings. The Mexican military detained a member of the Barrio Azteca gang, which works for the infamous Gulf drug cartel on both sides of the border. The suspect was identified as Ricardo Valles de la Rosa, 42, a resident of both Ciudad Juarez and El Paso.
Barrio Azteca is a U.S. prison gang that later found its roots in El Paso and Ciudad Juarez.
The Justice Department declined to comment on the Ciudad Juarez killings; the Department of Homeland Security did not return messages seeking comment.
The Mexican Embassy in Washington condemned the killings but did not respond to a follow-up request for comment about whether the Americans had been targeted intentionally. In a statement, it said the Mexican government would "work closely" with its U.S. counterparts "to track down those responsible for these killings so justice can be served."
The U.S. Drug Enforcement Administration would not comment specifically on the case but said "the violence we have been seeing is a signpost of the success that our very courageous Mexican counterparts have had in attacking those drug-trafficking organizations."
The drug rings "are acting like caged animals because they are caged," said DEA spokesman Rusty Payne. "They have lost roots, and they have lost control. The Mexican government has gone after them, and this is the reaction from drug organizations that are in disarray."
On March 14, the State Department issued its strongest travel warning to date for U.S. citizens planning on traveling to Mexico. The department also approved the departure of the dependents of U.S. personnel from consulates in the northern Mexican border cities of Tijuana, Nogales, Ciudad Juarez, Nuevo Laredo, Monterey and Matamoros.
It warned that the cartels are using automatic weapons and grenades, that "large firefights" have taken place in towns and cities across Mexico and that public shootouts have taken place during daylight hours in shopping centers and other public venues.
The department said drug criminals have followed and harassed U.S. citizens traveling in their vehicles, that travelers on major highways have been targeted for robbery and violence and that others have been caught in incidents of gunfire between criminals and Mexican law enforcement.
"While most crime victims are Mexican citizens, the uncertain security situation poses serious risks for U.S. citizens as well," it said.
Since January 2008, nearly 5,000 homicides have been committed in Ciudad Juarez alone, making it one of the most violent cities in the world. The bodies of some of those killed have been dumped in schoolyards and other public venues. Many of the victims were ambushed. Others were killed with grenades and AK-47 assault rifles.
Still others have been decapitated, their bodies hung from bridges - along with banners with warning messages from the cartels.
Mr. Calderon declared war against the Mexican cartels in 2006 and has committed more than 40,000 Mexican soldiers to the fight, although the violence continues to escalate. To date, the cartels in Mexico have killed more than 17,000 people.
At the core of the drug fight are the Sinaloa and Gulf drug cartels, along with Los Zetas, a group led by former Mexican military officers. They seek to control long-established smuggling corridors into this country, over which billions of dollars in illicit narcotics travel annually.
Secretary of State Hillary Rodham Clinton traveled to Mexico City this month as part of a delegation to underscore concern over Mexico's drug violence.
"These appalling assaults on members of our own State Department family are, sadly, part of a growing tragedy besetting many communities in Mexico," Mrs. Clinton said.