While Caro Quintero was only ever sentenced in Mexico for the killing of U.S. Drug Enforcement Administration agent Enrique “Kiki” Camarena and Mexican pilot Alfredo Zavala Avelar in 1985, his gang apparently killed as many as six U.S. citizens in the western city of Guadalajara around the same time.

John Clay Walker, then 36 and a writer who had moved to Guadalajara to finish a book, was one of them.

“We were both very glad to hear that (Caro Quintero) had been captured, and it also brought back a lot of trauma for us,” said Lannie Walker. “My sister and I have lost almost 40 years with our father, there is nothing that can make up for that.”

The U.S. writer and his friend Alberto Radelat, a dental student from Fort Worth, Texas, had walked into “The Lobster,” a high-end Guadalajara seafood restaurant, to celebrate Walker’s planned return to the United States.

They did not know that Caro Quintero and his companions were holding a private party in a back room of the restaurant.

“Our father was an American citizen with no involvement in the Mexico-United States drug war, he was an innocent bystander that unwittingly became caught in the crosshairs of a dangerous drug cartel,” said Lannie Walker. “They began questioning my father and Al, asking them what they knew about the drug enforcement agents in Mexico, what they knew about the investigation. My father knew nothing, he was an innocent writer. They tortured him with an icepick for an hour.”

Mike Vigil, the DEA’s former chief of international operations, said “Caro Quintero was one of those individuals that because he now had power, he had wealth, he crossed the line many times in terms of the people that he killed.”

Describing what occurred at the restaurant, Vigil said “they looked out and they saw the two Americans and they immediately through their paranoia as well thought that they were DEA agents. They took him into the back and stabbed to death.”

The bodies of Radelat and Walker were found wrapped in carpet in June 1985, nearly five months after they disappeared.

In December 1984, two young American couples were walking door to door in Guadalajara, trying to spread their faith as Jehovah’s Witnesses. The four were abducted and never seen again.

Two state police officials later said that they helped kidnap and kill the couples on the order of Caro Quintero and fellow capo Ernesto Fonseca Carrillo. They apparently inadvertently knocked on Fonseca Carrillo’s door as they proselytized.

Vigil, who was in Mexico and worked on Camarena’s case at the time, explained why the investigation focused on the killing of the DEA agent.

“I think that the DEA concentrated on the Kiki Camarena case and then the drug trafficking charges. I don’t think that the DEA, it was not that they weren’t interested in the other murders, but, you know, that probably would have fallen into the jurisdiction of maybe another agency,” Vigil said.

“One of the things that we were really focused on was bringing these individuals to justice simply because the DEA is committed that if one of the agents is murdered, we will hunt these people down to the end of the earth and not spare any expenditure, any resources or any activity that we have to do to get the job done,” he said.

Lannie Walker says that “if Caro Quintero is extradited to the U.S. and is convicted and punished here, that would be a small amount of justice.”

They likely will not come quickly. Caro Quintero’s lawyers filed measures with the court - and the judge agreed - that would ensure he goes through the full extradition process and will have the possibility of the corresponding appeals if necessary. Extradition for former Sinaloa cartel leader Joaquin “El Chapo” Guzman took a year.

“We do have hope,” she said. “But we are very aware of how the Mexican government and the Mexican judicial system has worked, you know, as far as our fathers’ case is concerned up until now. So we do have hope but we are nervous that what happened in 2013 could happen again.”