Oscar Osvaldo Garcia Montoya, 36, is allegedly the leader of "The Hand with Eyes" drug gang, known for extreme violence including decapitations. The gang is one of the groups blamed for bringing the drug violence typical of northern Mexico to Mexico City and its surrounding areas.
The bushy-haired Garcia gazed coolly when he was paraded before journalists Thursday, held firmly by two masked police officers.
Garcia is known as "El Compayito" after a popular Mexican talking hand-puppet character created by an entertainer who dresses up his hand and puts eyes on it. The crime gang apparently took its name from Garcia's puppet nickname.
"In the first declarations that have been gathered, El Compayito and-or 'The Hand with Eyes,' has acknowledged having participated personally in 300 murders and ordering another 300," said State of Mexico Attorney General Alfredo Castillo during a news conference.
Castillo said Garcia is a deserter from the Mexican marines who worked as a bodyguard for major cartel figures including Edgar Valdez, aka "La Barbie," a top assassin for the Beltran Leyva cartel until he was arrested in 2010.
The Associated Press contributed to this report.