Velasquez surrendered to authorities in 1992, telling a reporter at the time, "I don't owe anything to anybody. I haven't done anything wrong."
But in jailhouse interviews, he admitted several times to killing about 300 people, including soldiers, police officers, rival cartel members and civilians. He also confessed to masterminding the killings of more than 3,000 other people, most of them civilians.
Some of his victims died in car bombings in cities across Colombia including Bogota; Medellin, his cartel's home base; and Cali.
Velasquez was also responsible for a number of high-profile kidnappings, among them that of Attorney General Carlos Mauro Hoyos in January 1988. Velasquez confessed that he killed Hoyos in captivity.
Also in January 1988, Velasquez kidnapped Bogota mayoral candidate Andres Pastrana. Pastrana survived the ordeal and went on to become the 57th president of Colombia, serving from 1998 to 2002.
The victim and his kidnapper met again in 2012. Still in prison, Velasquez apologized to Pastrana and his family.
"I ask you for forgiveness from the bottom of my heart," he told Pastrana, "for what the Medellin cartel did, for risking your very important life."
He also told Pastrana he dismembered some of his victims, something he says he deeply regrets as a man who's turned his life to God.
Velasquez spent 22 years in prison, three-quarters of his sentence for the murder of presidential candidate Luis Carlos Galan in 1989, the only murder for which he was convicted.
The victim's family has forgiven him.
"He was sentenced for my father's murder," said Juan Manuel Galan, the victim's son and a liberal senator. "He gave us the truth and asked for forgiveness. In my case, I forgive him."
Velasquez told local media that he fears for his life as a free man and that there's an 80% chance that his many enemies will kill him, especially those members of the Medellin cartel whose names and crimes he disclosed to authorities.
Relatives of many of his victims angrily protested Velasquez's release, saying that 22 years in prison was not punishment enough for the countless atrocities he committed during the narcoterrorism era and cocaine turf wars of the '80s and '90s.
But Colombian Sen. Armando Benedetti said that Velasquez was being freed for good conduct, as any other prisoner would, and that his release complied with the law.
"The debate about his release has to center on the fact that in Colombia, we respect the rule of law, and we abide by the constitution, even in those cases where we are in disagreement with the consequences of some decisions," Benedetti said.
source: cnn.com By Fernando Ramos and Rafael Romo