Theories abound about what led to the rift between the Gulf Cartel and Los Zetas , but several years ago -- Campbell estimates it was about 2008 -- Los Zetas broke off , `` unleashing a tremendous wave of violence all over Northeast Mexico . '' Arrest could mean death knell for Los Zetas , ex - intelligence officer says . Los Zetas - Gulf Cartel split unleashed ` ` spread all over Northeast Mexico '' Death of U.S. agent , sniper fire brought added casualties , Mexican focus on group . Los Zetas include drug and human smuggling , kidnapping on criminal activities .
Arrest could mean death knell for Los Zetas , ex - intelligence officer says . Los Zetas - Gulf Cartel split unleashed ` ` spread all over Northeast Mexico '' Death of U.S. agent , sniper fire brought added casualties , Mexican focus on group . Los Zetas include drug and human smuggling , kidnapping on criminal activities .