The paramilitary groups commanded by Mancuso fought the guerrillas (mainly EPL, FARC and ELN), and financed their activities by receiving donations from land owners, drug trafficking, extortions and robbery.

In a surprise move by the Colombian government, Mancuso, along with 13 other top members of the AUC was extradited to the United States to stand trial on drug trafficking charges.

He studied civil engineering in the Pontificia Universidad Javeriana and later farming administration in the Escuela de Formación Técnica Agrícola in Bogotá.

On January 15, 2007, Mancuso admitted his crimes to a Colombian court following a deal that his attorneys were pursuing to preclude his extradition to the United States for drug trafficking.

According to the country's Justice and Peace Law, Mancuso should reveal trafficking routes and drug contacts in order to completely fulfill the deal.

It also closes the door to the possibility that victims can participate directly in the search for truth about crimes committed during the conflict, and limits access to reparations for damages that were caused.

"[9] A 2016 investigation by the New York Times found that the extradited paramilitaries, including Mancuso, had been given special treatment by the US justice system, serving shorter sentences than would be expected for drug-trafficking offences of that magnitude; a number of judges and prosecutors involved in trying the cases publicly stated their admiration for the political cause of the AUC, which they saw as a mitigating factor.

On November 18, 2008, Revista Semana reported on Mancuso's declarations about the 1997 El Aro massacre, in which he stated that the AUC had received logistical help from the Colombian military and police.

He acknowledged the assassination of the humorist Jaime Garzón in 1998 on the orders of the Colombian army, the massacres of political opponents carried out jointly with the armed forces, his participation in the practice known as "false positives" by assassinating civilians that the military then passed off as guerrillas who had died in combat, the use of crematoria to make some of the victims disappear and mass graves in Venezuela containing hundreds of bodies that the unit he commanded made disappear.

He was surrendered to the custody of the Colombian authorities and is expected to ask for a reduced prison sentence in return for his cooperation in war crimes investigations.

[17] On June 5, 2008, several Colombian media outlets reported police in Montería found a suitcase allegedly containing Mancuso's shadow administration, revealing more property owned by the warlord through secret associates.