(AP) — It started with a forgetful hotel guest — $42,000 left in a room in Boulder, Colo. It ended two decades later — the leader of a fearsome Mexican cartel sent to prison for 17 years.

The discovery in 1988 eventually led authorities to hundreds of pounds of marijuana and sparked an investigation of the leader of a drug ring that authorities say exported more than 100 tons of marijuana to the U.S. between 1985 and 1988.

That case reached its climax Thursday with the sentencing of a Miguel Angel Caro Quintero who led the Sonora Cartel to 17 years in federal prison for racketeering in Colorado and one count of conspiracy to distribute marijuana in Arizona.

The 46-year-old Caro Quintero's cartel was tied to the 1985 torture and killing of an undercover Drug Enforcement Administration agent Enrique "Kiki" Camarena Salazar, but authorities never directly linked it to him. His brother, Rafael Caro Quintero, is in prison in Mexico for the slaying.

A. James Kolar, then the sergeant in charge of the Boulder narcotics unit, said police were called to the hotel after a maid found the money.

"He apparently went off and left the money in the room," Kolar recalled after Thursday's sentencing. "We were checking it out and he came back to get it."

Police didn't immediately arrest the man, but they followed him to a grocery store parking lot where they discovered an RV packed with nearly a half ton of marijuana. Police then questioned the suspect who said he was working for the cartel.

Following that trail, the investigation led to several suspects in Colorado and in Arizona, Kolar said.

"We had no idea that Mr. Quintero was involved," said Kolar, now the police chief in Telluride, a ski resort town in southwestern Colorado. "It wasn't until we got indictments from federal agents that witnesses started providing information that led to Quintero."

Investigators have been reluctant to speak about the case until now.

Phoenix DEA Special Agent in Charge Elizabeth Kempshall said the feds knew about the drug cartel's operations and were working to build a case and help from local law enforcement still plays a role.

"Going against these drug traffickers, whether it's today or 20 years ago, it's important that we leverage all the resources and the talent that these federal and local law enforcement agencies bring, that we go after them with everything we can," she said.

Enrique Camarena Salazar was working for the DEA out of Guadalajara, Mexico, when he was kidnapped on Feb. 7, 1985, by five armed men who threw him into a car and sped away. He was tortured and beaten to death. The 37-year-old agent left behind a wife and three children.

Quintero's brother was convicted in Camarena's slaying. After his brother's arrest, federal authorities say Quintero took over the operation that smuggled thousands of tons of marijuana and cocaine into the U.S. in the 1980s.

"There was a lot of commitment by the DEA so that Kiki's death was not in vain," said Kempshall of the length of the investigation and time it took to prosecute Caro Quintero.

Added Jeffrey Sweetin, Denver DEA special agent in charge: "It gets personal when an organization has been tied to the death of a DEA agent.

"It makes this one a little bit more personally satisfying," he said of Quintero's guilty plea and sentence.

Prosecutors said under Caro Quintero's direction, the cartel exported two to four tons of marijuana a month to Colorado between 1985 and 1988. It was distributed throughout the United States by aircraft and vehicle.

Following the investigation sparked by the hotel room cash discovery, Caro Quintero was indicted in Colorado in 1990 on charges that included smuggling marijuana in half-ton amounts in 1987. The indictment alleged the gang dealt with large amounts of cash and that associates once carried $1.5 million in seven grocery bags in Boulder.

Prosecutors say Caro Quintero also conspired with two other people to import thousands of pounds of marijuana into Arizona and was recorded on the phone trying to sell marijuana to an undercover drug agent.

"The thing about this case is it demonstrates that it's not a matter of whether we're going to get these guys, it's a matter of when," Sweetin said.

Caro Quintero was arrested in December 2001 in Los Mochis, Mexico, and served a drug sentence in that country. He was extradited to the U.S. last February.

Camarena's slaying was commemorated each year by students in Calexico, Calif., where he attended high school. Students wore red ribbons in the agent's memory. The remembrance expanded and was made national by Congress in 1988 as Red Ribbon Week, during which drug and violence prevention campaigns are held in schools each October.

Camarena was a native of Mexicali, Mexico. He served in the U.S. Marine Corps and the Calexico and El Centro, Calif., police departments before joining the DEA.

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