MEXICO CITY (AP) – Drug lord Ernesto “Don Neto” Fonseca Carrillo, who was convicted in the 1985 killing of a U.S. Drug Enforcement Administration agent, was transferred from prison to house arrest Thursday to serve out the remainder of his sentence.

The 86-year-old co-founder of the Guadalajara Cartel was taken overnight to a house in Mexico State, which borders the capital, and was entrusted to the care of his wife, federal prisons chief Eduardo Guerrero said in comments broadcast by the Televisa network.

Guerrero said Fonseca will be required to wear an electronic bracelet and the home will have four guards posted around the clock, as well as closed-circuit cameras monitoring the perimeter. He said officials fought for over a year to keep Fonseca in prison but ultimately had to obey a judge’s order of house arrest.

“From the government’s perspective, we believe it is not right that someone who did so much damage to this country is today serving the end of this sentence on the outside. … He did a lot of damage to society and he should still be, according to all the studies, inside a federal prison,” Guerrero said.

The prisons chief added that authorities made various security checks at the house including ensuring there was no tunnel through which Fonseca could potentially escape.

Fonseca, who was convicted in the 1985 kidnapping, torture and murder of DEA agent Enrique “Kiki” Camarena, has nearly 10 years remaining on his 40-year sentence. His family successfully petitioned a judge to grant him house arrest for the remainder due to his poor health and advanced age.

“We exhausted all legal recourses we had at our disposition to prevent Ernesto Fonseca from getting out,” said Guerrero, adding that he had no knowledge of whether Fonseca may still be dangerous or involved in a criminal organization.

Another co-founder of the Guadalajara Cartel, Rafael Caro Quintero, was released from prison in 2013 after an appeals court overturned his own conviction in Camarena’s killing on jurisdictional grounds. Mexico’s Supreme Court annulled that ruling three months later and a warrant was issued for Caro Quintero to be rearrested, but he remains at large. The U.S. government offered a $5 million reward for information leading to his recapture.