CIUDAD JUAREZ, MEXICO (By William Booth, Washington Post) April 4, 2010 ― A cross-border drug gang born in the prison cells of Texas has evolved into a sophisticated paramilitary killing machine U.S. and Mexican officials suspect is responsible for thousands of assassinations here, including the recent ambush and slaying of three people linked to the U.S. consulate.

The heavily tattooed Barrio Azteca gang members have long operated across the border in El Paso, dealing drugs and stealing cars. But in Ciudad Juarez, the organization now specializes in contract killing for the Juarez drug cartel. According to U.S. law enforcement officers, it may have been involved in as many as half of the 2,660 killings in the city in the past year.

Officials on both sides of the border have watched as the Aztecas honed their ability to locate targets, stalk them and finally strike in brazen ambushes involving multiple chase cars, coded radio communications, coordinated blocking maneuvers and disciplined firepower by masked gunmen in body armor. Afterward, the assassins vanish, back to safe houses in the Juarez barrios or across the bridge to El Paso.

"Within their business of killing, they have surveillance people, intel people and shooters. They have a degree of specialization," said David Cuthbertson, special agent in charge of the FBI's El Paso division. "They work day in and day out, with a list of people to kill, and they get proficient at it."

The special agent in charge of the Drug Enforcement Administration (DEA) in El Paso, Joseph Arabit, said, "Our intelligence indicates they kill frequently for a hundred dollars."

The mayor of Juarez, José Reyes Ferriz, said the city is honeycombed with safe houses, armories and garages with stolen cars for the assassins' use. The mayor received a death threat recently in a note left beside a pig's head in the city.

Arabit said investigators have no evidence to suggest the Barrio Azteca gang includes former military personnel or police. It is, however, working for the Juarez cartel, which includes La Linea, an enforcement element composed in part of former Juarez police officers, according to Mexican officials.

"There has to be some form of training going on," said an anti-gang detective with the El Paso sheriff's department, who spoke on the condition of anonymity because of the nature of his work. "I don't know who, and I don't know where. But how else would you explain how they operate?"

On March 13, Lesley Enriquez Redelfs, 35, who worked for the U.S. Consulate in Juarez, and her husband, Arthur Redelfs, 34, a deputy in the El Paso sheriff's department and a detention officer at the county jail, were returning home to El Paso from a children's party sponsored by the U.S. consul in Juarez. As their white sport-utility vehicle neared the international bridge that sunny Saturday afternoon, they were attacked by gunmen in at least two chase cars. When police arrived, they found the couple dead in their vehicle and their infant daughter wailing in her car seat. The intersection was littered with casings from AK-47 assault rifles and 9mm guns.

Ten minutes before the Redelfs were killed, Jorge Alberto Ceniceros Salcido, 37, a supervisor at a Juarez assembly plant whose wife, Hilda Antillon Jimenez, also works for the U.S. Consulate, was attacked and slain in similar style. He had just left the same party and was also driving a white SUV, with his children in the car.

According to intelligence gathered in Juarez and El Paso, U.S. investigators were quick to suspect the Barrio Azteca gang in connection with what President Obama has called the "brutal murders." What was unclear, they said, was the motive. U.S. diplomats and agents have declined to describe the killings as a targeted confrontation with the U.S. government, which had been pushing to place U.S. drug intelligence officers in a Juarez police headquarters to more quickly pass along leads.

Five days after the consulate killings, the DEA unleashed in El Paso a multiagency "gang sweep" called Operation Knockdown to gather intelligence from Barrio Azteca members. Over four days, officers questioned 363 people, including about 200 gang members or their associates, and made 26 felony arrests.

Soon after, the Department of Homeland Security issued a warning the Barrio Azteca gang had given "a green light" to the retaliatory killing of U.S. law enforcement officers.

Authorities were especially interested in Eduardo Ravelo, a captain of the Barrio Azteca enterprise allegedly responsible for operations in Juarez. In October, the FBI had placed Ravelo and his mug shot on its 10-most-wanted list, though they warned Ravelo may have had plastic surgery and altered his fingerprints. Ravelo is still at large.

DEA agents say 27 Barrio Azteca members were detained as they tried to cross from El Paso to Juarez during Operation Knockdown, evidence of gang members' fluid movement between the two countries.

This week, authorities announced Mexican soldiers, using information from the FBI and other sources, had arrested Ricardo Valles de la Rosa, an Azteca sergeant, in Juarez.

Valles's confession was obtained at a military base where he was allegedly beaten, according to his attorney, a public defender. He has not been charged in the consulate killings, though he is charged with killing rival gang members, including members of an enterprise known as the Artistic Assassins, or "Double A's," who operate as contract killers for the Sinaloa cartel. Sinaloa is vying for control of billion dollar drug-trafficking routes through the Juarez-El Paso corridor.

In his statements, Valles said he was told through a chain of letters and phone calls from Barrio Azteca leaders in the El Paso county jail and their associates gang leaders wanted Redelfs, the El Paso sheriff's deputy, killed because of his treatment of Azteca members in jail and his alleged threats against them.

Valles said he tracked down Redelfs at the children's party and then handed off the hit to others. He said the killing of the factory supervisor was a mistake because he was driving a white SUV similar to Redelfs's.

El Paso County Sheriff Richard Wiles said in a statement Valles was a career criminal and denied Redelfs had mistreated inmates. Wiles stressed the motives remain unknown.

Fred Burton, a former State Department special agent and now a security adviser for the Texas government, said he is suspicious of attempts to underplay the killings. "These were targeted hits done by sophisticated operators," he said. "But it is not politically expedient for either side to say criminal organizations were behind this. That is a nightmare scenario for them."

Mexican officials say Valles, 45, was born in Juarez but grew up in El Paso, where he lived for 30 years. Nicknamed "Chino," he was a member of the Los Fatherless street gang in El Paso. In 1995, he was convicted of distributing drugs and spent 12 years in eight U.S. federal prisons, where he met an Azteca gang leader. After his release, he was deported to Mexico and began working with the Aztecas in Juarez.

The theory the carnage in Juarez is being stoked by rival gangs of contract killers -- the Barrio Aztecas and the Artistic Assassins -- each working for rival drug cartels makes sense to many observers.

The gangs are a binational phenomenon whose members exploit the mistrust between U.S. and Mexican law enforcement, said Howard Campbell, a professor at the University of Texas in El Paso and an expert on the drug trade.

"They use the border to their advantage," Campbell said.