Initially, police arrested Francisco Miguel N. for carrying a gun and drugs. But once he was in custody, the 16-year-old from Sinola made a confession: He was an assassin for Los Mazatlecos, a criminal group attached to the Beltran Leyva drug cartel. Now prosecutors believe the teen participated in at least 50 murders, Reuters reports. Francisco Miguel, who went by "El Nino," says he used an AK-47 and pistol to carry out the killings, and lists among his victims police, farmers, and even one musician. He is not to be confused with this teen cartel hitman.