A patriarch of the drug-trafficking far-right paramilitary bands that killed thousands in Colombia has been released from prison after serving less than 10 years.

Officials said Friday that 74-year-old Ramon Isaza was freed last week from a Medellin prison. Isaza was a founder of the militias created in the early 1980s by ranchers and traffickers seeking to protect themselves from guerrilla kidnappings and extortion.

The groups formed death squads that targeted suspected rebel sympathizers, union activists and representatives of landless peasants. They were also in the cocaine trade.

Isaza surrendered in 2006 under a peace pact that stipulated that paramilitary warlords confess their crimes in exchange for prison terms of no more than eight years.

When his time came to confess, Isaza complained of serious memory lapses.