Angel de Jesús Pacheco, alias "Sebastian," is generally recognized as being responsible for a great deal of the mayhem that afflicted northeast Antioquia throughout 2009 and 2010. Originally from the municipality of Caucasia in the Antioquia department, Pacheco began as a mid-ranking paramilitary commander in the Central Bolívar Bloc. Following the extradition to the United States of the bloc’s leader, Carlos Mario Jiménez, alias "Macaco," Pacheco saw an opportunity to seize control of criminal operations in northern Antioquia.

Soon Pacheco was facing down a new enemy: Daniel Rendon Herrera, alias "Don Mario," leader of an AUC faction that later began calling themselves the Urabeños. With a band of loyal paramilitaries, Pacheco enlisted the help of the Paisas to help him resist the advance of the Urabeños into Antioquia. The Paisas drew most of their recruits from another paramilitary faction, the Mineros Bloc, in their time reluctant allies of Macaco and his crew. This suspicion carried over into the new generation of drug runners, and Pacheco and the Paisas did not have a comfortable alliance. 

By 2009, Pacheco decided to switch sides. Pacific-based gang the Rastrojos were also looking to enter Antioquia's Bajo Cauca region, an area with a strong regional identity that does not take to strangers. The Rastrojos recruited Pacheco and his men to fight for them in the area, and Pacheco took their offer. Afterwards, his faction began fighting both the Urabeños and the Paisas. As a result of the gang war, Bajo Cauca's most violent municipality, Caucasia, registered 224 murders per 100,000 inhabitants in 2009, among the highest in the country. 

A brutal man who relied on violence and intimidation to keep his followers in line, Pacheco did not inspire natural loyalty. On July 25 2011, his two bodyguards shot him five times, tied his body to a tree, then turned themselves in to the police. At the time of his death, Colombian authorities offered a $600,000 reward in return for information on his whereabouts.