Colombian conflict dialogue, but President Barco sent an ultimatum to the guerrillas and demanded that they immediately disarm or face military retaliation. Regional guerrilla and Army skirmishes created a situation where each violation of the ceasefire rendered it null in each location, until it was rendered practically nonexistent. By 1990, at least 2,500 members of the FARC-founded Patriotic Union had been murdered, according to historian Daniel Pecáut, leading up to that year's assassination of presidential candidate Bernardo Jaramillo Ossa. The Colombian government initially blamed drug lord Pablo Escobar for the murder but journalist Steven Dudley argues that many in the UP pointed
Pablo Escobar joined the manhunt for Escobar. They trained and advised a special Colombian police task force known as the Search Bloc, which had been created to locate Escobar. Later, as the conflict between Escobar and the governments of the United States and Colombia dragged on, and as the numbers of Escobar's enemies grew, a vigilante group known as "Los Pepes" (Los Perseguidos por Pablo Escobar, "People Persecuted by Pablo Escobar") was formed. The group was financed by his rivals and former associates, including the Cali Cartel and right-wing paramilitaries led by Carlos Castaño, who would later fund the Peasant Self-Defense Forces