The Mexican Sinaloa drug cartel hired a hacker to track and surveil the FBI, then used that information to intimidate and even kill witnesses.

The Sinaloa drug cartel in Mexico hacked the phone of an FBI official investigating kingpin Joaquín “El Chapo” Guzmán as part of a surveillance campaign “to intimidate and/or kill potential sources or cooperating witnesses,” according to a recently published report by the Justice Department.

A hacker hired by a notorious Mexican drug cartel reportedly accessed an FBI official’s phone records and surveillance cameras to help find and kill FBI informants.