Jorge Humberto Victoria demobilised five years ago under a peace deal with the government, but did not turn himself in at the time. Mr Victoria is believed to be a key witness in the 1997 massacre of villagers in Mapiripan, in the east of the country. The Colombian military was found guilty of colluding in the massacre by the Inter-American Court of Human Rights. Mr Victoria handed himself in to the Prosecutor\'s office in Barbosa, in north-western Antioquia province on Tuesday. He was in charge of a paramilitary group in the eastern plains of Colombia from the early 1990s to 1999. Brutal massacre In 1997, the paramilitary group he commanded committed a massacre of an undetermined number of villagers in Mapiripan, in Meta province. The bodies of the victims were dismembered and thrown into a river, making it almost impossible to determine the exact number of people killed. Massacres by paramilitaries such as that in Mapiripan were not uncommon as the far right-wing groups moved into villages and killed anyone they suspected of being members of, or of supporting left-wing rebel groups. Carlos Castano, the founder and highest commander of the paramilitary umbrella group United Self Defence Forces of Colombia (AUC), said the paramilitaries had killed 49 people in Mapiripan in a massacre lasting from 15 to 20 July 1997. Human rights groups said the killing could not have been committed without the knowledge of local troops who manned the checkpoints leading to the village. The case was taken to the Inter-American Court of Human Rights, which ordered the Colombian state to pay $8m to the victims of the massacre after ruling that members of the military had colluded in the killing. Military collusion Two years ago, a Colombian court sentenced former Gen Jaime Humberto Uscategui to 40 years in jail for his role in the massacre. The court said he had ignored pleas for help from the villagers and local officials as the paramilitaries went on their killing spree. But after handing himself in on Tuesday, Mr Victoria said he had been \"surprised\" by the sentence handed out to Gen Uscategui. \"They link him as a collaborator to the AUC in the eastern plains, but I never had any contact with him during my time as a commander or the boss of the structure there, I never talked to him and he never knew of my actions there,\" Mr Victoria said shortly after handing himself in to the Prosecutor\'s office on Tuesday. Under the peace deal reached between the government and the AUC under which he demobilised in 2006, Mr Victoria will be expected to give evidence of his actions during his time as a paramilitary leader. The Prosecutor\'s Office hopes he will be able to shed further light on the massacre in Mapiripan. They will be particularly interested in how many people he says his men killed, especially since the controversy surrounding the number of victims recently resurfaced. \'False victims\' In October, the Prosecutor\'s Office said that after questioning other demobilised paramilitaries who had taken part in the massacre, they believed the number of victims was only around 10 rather than 50. And on Thursday, Justice Minister Juan Carlos Esguerra said the state would prosecute a number of \"false victims\", who he said had fraudulently claimed reparation money by pretending relatives of theirs had been killed in the massacre. Colombia has also taken the case back to the Inter-American Court of Human Rights in an attempt to get the court to revise the number of victims down. The court has given Colombia three months to present evidence of cases of \"false victims\".