Gunmen shot dead three men and a woman in Monterrey on Wednesday and left graffiti on a wall at the crime scene reading "Commander X20, at your orders, [signed] CDG [Gulf Cartel]", according to local media.
Factbox: Worst atrocities in Mexico's drug war
Slideshow: Mexico's drug war, drug culture
Monterrey is Mexico's most affluent city and has long been seen as a model of economic development in Latin America. But it has been ravaged by drug warfare over the last three years.
-- Reuters
