A man in Central California charged with nine contract killings confessed to investigators that he killed up to 40 people, over a span of decades.

Jose Manuel Martinez told investigators that he carried out the killings while working as an enforcer for a drug cartel, according to Errek Jett, the district attorney in Lawrence County, Ala.

Martinez was apprehended last year when crossing the border from Mexico into Arizona and arrested on a charge of shooting and killing a man in Alabama in March 2013, reports The LA Times.

The killings executed by Martinez took place from 1980 to 2011 in Tulare, Kern, and Santa Barbara counties. Victims ranged in age from 22-56.

In 1980, a man was shot dead while driving to work in the morning. Two years later, two men were shot while working on a ranch and one survived. In 2000, a man was shot while his four children were home sleeping.

Martinez told authorities that he joined the cartel at 16 years old and earned 25% on collected debts, in addition to extra incentive for his murders, according to The NY Daily News.

Investigators didn’t believe Martinez, until he provided them with details of the gruesome murders.

Martinez is currently being held in Alabama, awaiting a trial in June for his recent murder in Alabama and nine murders in California.