His nickname came from the favoured weapon he used on his victims.Member of a family already involved in crime, Guerrero and his siblings were known as Los Cuchillos (the Knives) due to their habit of sporting those weapons.
He joined the underground crime world during his teenage years as a member of the private militia of drug lord Gonzalo RodrĂguez Gacha, aka El Mexicano.
Following the death of El Mexicano, Guerrero escaped to the department of Guaviare where he joined the paramilitary groups that were active in the region.
These paramilitary groups grew in number and influence and came to be called the Bloque Centauros of the United Self-Defense Forces of Colombia (AUC) under the command of Miguel Arroyave.
Guerrero had ascended through the ranks and by the end of the 1990s he was the commander of the Bloque in the Guaviare department.