MEXICO CITY, Aug 31, (AP): Osiel Cárdenas Guillén, one of Mexico’s most-feared drug lords, has been released from a U.S. prison after serving most of a 25-year prison sentence, authorities confirmed Friday. A US Bureau of Prisons official said Cárdenas Guillén had been released from prison and was placed in the custody of the US Immigration and Customs Enforcement. That would normally suggest he would be deported back to Mexico.

A Mexican official who was not authorized to be quoted by name said Cárdenas Guillén faces two arrest warrants in Mexico, making it likely he would be detained upon arrival. The former head of the Gulf cartel was known for his brutality. He created the most bloodthirsty gang of hitmen Mexico has ever known, the Zetas, which routinely slaughtered migrants and innocent people.

Cárdenas Guillén was sentenced to 25 years in prison in 2010 and ordered to forfeit tens of millions of dollars. It was not clear why he did not serve his full sentence, but he had been extradited to the US in January 2007. The 57-year-old native of the border city of Matamoros, Mexico, moved tons of cocaine and made millions of dollars through the Gulf cartel, based in the border cities of Reynosa and Matamoros.

He created the Zetas, a gang of former Mexican special forces soldiers who he recruited to become his private army and hit squad. They committed acts of terror that regularly involved slaughtering dozens of people, decapitating them or dumping heaps of hacked-up bodies on roadways. The Zetas lived on long after Cárdenas Guillén was captured in 2003. By 2010, the Zetas had formed their own cartel, spreading terror-style attacks across Mexico as far south as Tabasco until their top leaders were killed or arrested in 2012-2013.