Roberto Alvarez was jealous of the amount of time his girlfriend spent with the head of a crime family that dealt in millions of dollars of contraband, so he became a confidential informant for the Florida Department of Law Enforcement.

Not long after talking with the agents, the 38-year-old Alvarez was shot to death; his body was found in a pool of blood 15 feet from the bus he drove in his job shuttling tourists to the theme parks.

If it had been guns or drugs that Alvarez was snitching about, his unsolved murder would have had a familiar ring. But, in an only-in-Orlando scenario, Alvarez was helping investigators track down theme park tickets illegally purchased with fake or stolen credit cards.

A black market for park tickets has grown up in this theme park mecca, and illegal transactions occur every day in the heart of its fantasy fueled tourist district. Detective Kelly Boaz of the Orange County Sheriff's Office said illegal ticket sales are a multimillion-dollar business.

"There is a lot of money out there in this type of activity," said Boaz, who works in a seven-person special unit dedicated to the theme parks.

This underground market is an unintended consequence of annual ticket-price increases and the popularity of multi-day passes that have made the tickets very valuable. A single-day ticket to a park costs almost $60, while a four-day park hopper, granting entry into all four Disney parks in Orlando, can cost $220 a person.

"The theme parks have always been an incredible experience that some people treat as a commodity," said Universal Orlando spokesman Tom Schroder. "So as long as there have been theme parks and theme park tickets, there have been people trying to take advantage of that."

The black market also has been fueled by the proliferation of booths selling discounted tickets in almost every major hotel and restaurant, or in front of every tacky T-shirt shop, in Orlando's tourist district.

The number of booths has increased in recent years from several dozen to 200 or 300. Many of the booths are run by timeshare companies that use the tickets as an incentive to get tourists to see their properties. The booths can rent for as much as $15,000 a month.

"It's getting tougher and tougher. There's a lot more competition," said Fred Richard Pinner Jr., who operated a booth until recently.

The area's major theme parks -- Walt Disney World, Universal Orlando and SeaWorld Orlando -- often sell tickets discounted 10 percent off the regular gate price to timeshare companies, AAA and other tourism-related businesses. International tour companies get an even better deal from the theme parks -- as much as 20 percent off the gate price.

But those 20 percent-off contracts are limited and highly coveted. So companies with the international contracts, in violation of their agreements with the parks, often sell their tickets to middlemen ticket brokers or to booths that do not have the contracts and cannot get the discount. Those people then sell the tickets to the general public.

"It's all a big game out there," said Franklin Fox, who was once described by law enforcement as the ringleader of illegal ticket brokers. "Everybody knows what's going on."

Law enforcement agencies have tried to stop black market ticket-brokers much as they would drug dealers. They have targeted street-level sellers in an effort to catch those higher up the chain. They have used secret informants, surveillance and undercover agents posing as illegal ticket scalpers or clueless tourists.

"What we've been doing for the last few years is plugging the dam, going after the smaller dealers that we get to," Boaz said. "We have been trying for the last few years to work our way up to higher folks, but they've isolated themselves so well and have been under the radar for so long, it was difficult."

Some of the shady ticket dealers sell multi-day park tickets to tour groups at discounted prices provided the groups bring back the passes at the end of a single day. The passes are then resold at discount to other tour groups the next day, which is a second-degree misdemeanor for a first-time offender under Florida law, punishable by as much as 60 days in jail and a $500 fine.

Others, known by the police as "walkers," target tourists, most likely foreigners who are perceived as gullible, near the ticket booths at the theme parks. They then sell multi-day park passes that have days already used up, Boaz said.

"Many of the people at these booths are reputable, but there's a small percentage that engage in the resell of tickets," Schroder said.

Fox operated several booths that sold tickets to tourists along the busy tourist thoroughfares of International Drive and U.S. 192, yet he did not have a contract with many of the parks.

A close friend, who himself was caught in a sting operation last year and agreed to cooperate with authorities, persuaded Fox to purchase 210 tickets that supposedly had been illegally printed by a worker inside Universal Studios, according to court records. Fox, 70, took the bait and was charged with six counts of dealing in stolen property. Detectives seized $250,000 worth of theme park tickets from his office.

Fox pleaded no contest to two counts of petty theft late last year and was sentenced to a year of probation, which was terminated in June. He denied dealing in stolen tickets, calling his arrest a police set-up, and said he made a plea to avoid a trial.

Alvarez started talking, off and on, with authorities in late 2000 about schemes run by Victor Aquino, who used fake or stolen credit cards to purchase theme park tickets. The operation was made up of Aquino's family members and associates who came from South Florida and had roots in South America.

It included Aquino's teenage son, Amin, known by friends for a love of nightclubs and cocaine, who along with a former pizza cook, Mario Locasio, would buy tickets with stolen or fake credit cards provided by Victor Aquino. Aquino would then sell the tickets to Roberto Alvarez's girlfriend, Marilu Clement, who then supplied brokers like Franklin Fox, or different travel agencies, according to depositions from Clement's criminal case.

"Victor Aquino would hand her black bags and stacks of Disney tickets and things like this, which I thought was very suspicious and stuff," Locasio said in a 2003 deposition.

Alvarez was gunned down in July 2001. The group's schemes fell apart as members of the operation, one by one, were arrested in 2002.

Clement, who currently is serving probation for fraud, claimed she never knew the tickets were purchased with bad credit cards. Amin Aquino was sentenced to 31/2 years in prison for fraud, while his father, Victor, was sentenced to 51/2 years in prison for trying to run over a sheriff's deputy with a Mercedes.

Alvarez's murder may be an extreme case, and authorities will not comment because the case is still open and unsolved.

"The underlying fact of the investigation into his death indicates . . . that's the motive . . . because he was informing for the FDLE," homicide investigator Richard Lallament of the Orange County Sheriff's Office said in a 2003 deposition. "It was made to look like a botched robbery, but nothing is missing. It just doesn't make any sense."

Suspected kingpin Victor Aquino is in prison for trying to run down a sheriff's deputy with his Mercedes.Marilu Clement claimed not to know theme park tickets she handled were bought with bad credit cards.