On 9 November 1999, two agents from the United States Drug Enforcement Administration (DEA) and Federal Bureau of Investigation (FBI) were threatened at gunpoint and nearly killed in Matamoros, Tamaulipas, Mexico, by gunmen of the Gulf Cartel, a criminal group based in the area. The two agents traveled to Matamoros with an informant to gather intelligence on the operations of the Gulf Cartel. As they cruised through one of the properties owned by the criminal group, they noticed several vehicles following them. The agents were forced to a stop and were corralled by a convoy of eight vehicles, from which fifteen gunmen emerged and surrounded the agents' car. Some of them wore uniforms of the local police. Among the gunmen was the former kingpin Osiel Cárdenas Guillén, who recognized the inf