Authorities in Colombia say a prolific serial killer who confessed to murdering more than 190 children during the 1990s has died in a hospital where he was imprisoned.

He was 66.

Luis Alfredo Garavito was nicknamed “The Beast.”

He confessed to having murdered more than 190 children between the ages of 8 and 16, who were mostly from low-income families.

He kidnapped and abused his victims by posing as a monk, a homeless person or a street vendor.

The National Penitentiary Institute says that Garavito died in a hospital in Valledupar, in northern Colombia.

The cause of death has not been revealed.