Texas ? The eight bullets that leveled Jose Daniel Gonzalez Galeana outside his home just doors from El Paso’s police chief were fired at close range and left little doubt about their message.

Gonzalez, a Juarez cartel lieutenant shot on his quiet El Paso cul-de-sac this spring, was working for U.S. officials as a confidential informant, sources told The Associated Press, and experts suspect his slaying may be the first time assassins from one of Mexico’s violent drug gangs have killed a ranking cartel member on American soil.

Experts said the murder represents a growing brazenness of the cartels on this side of the border that will most likely lead to more deaths.

Gonzalez, a 37-year-old legal immigrant who lived with his family on a cul-de-sac in an expensive neighborhood, was shot May 15 in front of his spacious home. His wife, Adriana Solis, and the couple’s two children fled not long after.

Two federal officials and one local official told The Associated Press that Gonzalez was handing over information about cartel activities to U.S. Immigration and Customs Enforcement. One of those officials said federal investigators were monitoring Gonzalez’s activities and whereabouts.

Cartel-affiliated hit men have violently, and fatally, disciplined low-level, American-based drug dealers in the U.S. But El Paso police said Gonzalez was a lieutenant in the Juarez cartel, which traffics in marijuana, cocaine and heroin. The cartel was once among the most dangerous in Mexico, but has recently lost some standing because of arrests, deaths and infighting.