David Farrington, a U.S. Bureau of Diplomatic Security (DS) service agent, has been vexed by a troubling question for the past several years. He has reason to suspect a colleague deliberately failed to warn an American working at a U.S. consulate in Mexico that she was targeted for assassination by a drug cartel.

Farrington, a former Marine and 10-year veteran of the State Department’s security service, was the first agent to get to the scene of the March 13, 2010, Juarez murders—another car carrying a consulate employee was attacked as well—and caught the case, as they say in police lingo. But his revulsion quickly turned to consternation, and then obsession, when he began asking questions about the whereabouts of the consulate’s chief security officer that day. Eventually, he was taken off the case, according to State Department emails obtained by Newsweek, relieved of his badge and gun, and ordered to undergo a psychological fitness review. But he hasn’t given up.

Leslie Enriquez and her husband were gunned down as they drove away from a birthday party in the drug-and-violence-wracked border city of Juarez four years ago last month. Nearly simultaneously, another car leaving the party was sprayed with bullets, killing the husband of a Mexican employee of the U.S. consulate. A senior Mexican police official said later that a drug cartel enforcer who confessed to the murders claimed Enriquez was targeted because she was helping a rival gang with U.S. visas—an allegation denied by U.S. officials.

“I don’t have any reason to believe that they did believe that they did anything bad,” Farrington said of Enriquez and the other victims in a brief interview with Newsweek. “They were good people.” But he soon learned that the top regional security officer (RSO) in Juarez, Gregory V. Houston, had been asking around the consulate for the names of locally hired employees like Enriquez and one of the other victims that day. Farrington wondered why. He became even more suspicious when he learned that Houston got into serious trouble during a previous posting at the American Embassy in Sofia, Bulgaria…

Click here for the rest of the story.