MEXICO CITY (AP) — On a sunny winter morning in 1984, two young American couples dressed in their Sunday best walked door-to-door in the western Mexican city of Guadalajara, trying to spread their faith as Jehovah’s Witnesses. A few hours later they disappeared.

The next month an American journalist went out with a friend at the end of a year-long sabbatical writing a mystery novel. The two men also vanished.

Within 10 days, Drug Enforcement Administration agent Enrique ‘Kiki’ Camarena was kidnapped too, then tortured and killed by Mexico’s most powerful drug cartel, setting off one of the worst episodes of US-Mexico tension in recent decades. As DEA agents hunted for Camarena’s killers, some witnesses told them that the cartel had mistaken the other six Americans for undercover agents and killed them just like Camarena.

Cartel leader Rafael Caro Quintero walked free this month, 12 years early, after a local appeals court overturned his sentence for three of the murders. For the US and Mexico, Caro Quintero’s secretive, pre-dawn release has set off a frantic effort to get the drug lord back behind bars. For the families of the six Americans slain before Camarena, the decision has awakened bitter memories of the brutality that ushered in the modern era of Mexican drug trafficking.

“I just never imagined that this would happen, that Caro Quintero would be walking around free at the age of 60,” said journalist John Clay Walker’s widow, Eve, who lives in Atlanta. “There’s probably not been a day in the last 30 years that I haven’t missed my husband and wished that he was here to see the girls grow up.

“It was tough to do it alone but I kind of had the consolation of knowing that the responsible people were in prison and that they would stay there.”

The systematic killing of seven Americans in three months stands out even in the long and bloody history of the US-backed effort to quash Mexican drug trafficking. Tens of thousands of Mexicans have died, and dozens of Americans have been killed in cartel-related violence, often because of ties to people involved in drug trafficking. But assassinating US law-enforcement agents remains a taboo for most Mexican organised crime, as does the deliberate targeting of Americans with no ties to the drug war.

Walker was 37 when, according to some witnesses, he and his friend Alberto Radelat, a dentist from Fort Worth, Texas, walked into The Lobster, a high-end Guadalajara seafood restaurant where Caro Quintero and his companions were holding a private party.

Others have said Walker and Radelat were kidnapped off the street by Caro Quintero’s men as the cartel frantically hunted for the DEA agents behind an aggressive US push against large marijuana-growing and smuggling operations.

Walker and Radelat’s tortured bodies were found a little more than five months later in a park outside Guadalajara. Walker’s wife Eve helped identify the bodies. Their daughters Keely and Lannie were in elementary school at home in Minneapolis.

Under intense US pressure, Caro Quintero was arrested along with the two other heads of their Guadalajara-based drug organisation, splitting the monolithic cartel into smaller groups, including the Sinaloa cartel that has come to dominate Mexican drug trafficking along the Pacific Coast and much of the rest of the country.

Caro Quintero was sentenced to 40 years in prison for the murders of Camarena, Walker and Radelat, among other crimes.

On August 7, however, a three-judge federal appeals court in the western state of Jalisco found that he should have been tried in state, not federal, court, and vacated his sentence. The US has issued a new arrest warrant for Caro Quintero, and Mexico’s federal court says it is trying to find him again. Both governments say they disagree with the court decision and some US officials believe corruption is a likely explanation for the otherwise inexplicable ruling.

“It’s salt in a wound,” Keely Walker said of Caro Quintero’s release. “I thought it was all over with, he’s in prison.”

Her father was a Marine who was twice wounded by land mines in Vietnam and then worked as a newspaper journalist before taking his family to Mexico so he could write his book in a place where his pension could stretch further. He and his wife were befriended by Radelat, a dentist looking at taking classes at the main university in Guadalajara.

A Catholic by birth, Benjamin Mascarenas became a Jehovah’s Witness through conversion and met his wife Pat at a church function. They did janitorial work in Reno, Nevada, before moving to Guadalajara, where they house-sat for a wealthy acquaintance. Dennis and Rose Carlson moved from Redding, California, to support a church effort to spread their faith in Mexico.

The bodies of the two couples were never found.

Two state police officials said that they helped kidnap and kill the couples on the order of Caro Quintero and fellow capo Ernesto Fonseca Carrillo, according to agent Hector Berrellez, who ran the Los Angeles-based operation going after those involved in Camarena’s murder. The Jehovah’s Witnesses inadvertently knocked on Fonseca Carrillo’s door as they proselytised on December 2, 1984, Berrellez said. Believing they were undercover agents, the capos had their underlings capture and kill them, Berrellez said.

Some DEA veterans question that theory. James Kuykendall, the former agent in charge of the DEA office in Guadalajara, told The Associated Press that he has never seen any evidence to support it.

Many of the couples’ relatives do believe a version of the cops’ tale.

“I’ve got his picture right here,” said Benjamin Mascarenas’ mother Mercy, who is 86. “I’m looking at him and thinking of how wonderful it would be if they were alive. He was as sweet as pie and they just loved each other so much.”

Dennis Carlson was “just an all-around good person” dedicated to spreading his faith, recalled his brother, Stanley, a 58-year-old semi-retired mortgage banker.

“They just knocked on the wrong door and that led to the four of them being abducted,” Carlson said. “It makes me feel bad in general that this guy is running around if he is in fact responsible.”

He said his family rarely talked about the murders, and relied on their faith to cope with the pain.

“We’re not looking for any type of vindication or vindictiveness or anything of that nature because it’s not our place,” he said. “We feel that there’s a better world that awaits people of faith.”