The stunning new details offer a rare look at how technology can be exploited in the high-stakes battle between US law enforcement and the violent Mexican cartels that control illicit drug trade.

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.