Sebastian had forged ties with international trafficking organizations such as the Zetas in Mexico. Vargas worked alongside the Oficina’s founder, Diego Murillo, alias "Don Berna," in the vigilante movement against the famed drug trafficker Pablo Escobar in the early 1990s. He reportedly contributed valuable intelligence to authorities that helped lead to Escobar’s capture and death in 1993.
Vargas continued to manage the Oficina’s hitmen network up until Murillo’s extradition in 2008, while another leader, Maximiliano Bonilla, alias "Valenciano," mainly handled drugs trafficking operations. Bonilla and Vargas then fought each other for control of Medellin, especially the city’s so-called “micro-trafficking” business (which can bring in profits of more than $5.25 million a month), gambling and extortion schemes. Vargas’ center of influence was said to be Comuna 9.
- "International Narcotics Control Strategy Report - 2010," U.S. Department of State (March 2010).