Rosalio “Bart” Reta was only 13 when he carried out his first assassination for Mexico’s most violent and infamous drug cartel: Los Zetas. The gang’s long-time leader Miguel Treviño, who was captured just last week, was known for recruiting teenagers to carry out murders on both side of the US-Mexico border. Reta, now 23, was recruited as a sicario—a combination hit man and kidnapper—and worked in Laredo, Texas as part of a three-man cell, making $10,000 to $50,000 per hit, as well as perks including free cars. Today he’s serving a 70-year sentence in Texas prison for one of the 30 people he says he killed during his hitman career. In a video interview (below), he expresses guilt and regret for his past actions. “It gets to a point where I can’t even stand myself,” Reta tells Center for Investigative Reporting. “It’s eating me inside little by little, and there’s nothing I can do or say to justify my actions.”