A N T W E R P, Belgium, Feb. 12, 2004 -- They had just committed the perfect crime — sneaking past multiple levels of the world's top security to steal $100 million in diamonds.

But the group of brazen bandits then made the ultimate escape: calmly driving away from the scene near security patrols, armed guards and a police station housing the investigators who would soon be on their trail.

"They must have [had] an unbelievable kick at that moment," said Detective Agim DeBruycker.

The diamond world was astonished by the crime. Investigators have pieced together how the thieves managed to break into one of the world's most secure vaults, but some questions remain: Is the man in police custody the mastermind behind the scheme? And where in the world are all those diamonds?

A Burglary Worthy of Hollywood

The Antwerp diamond heist played just like a scene out of Ocean's Eleven or The Italian Job. It happened in the Belgian city's diamond district — hub of the world's diamond trade — at the Diamond Center, the district's largest building.

Police said the thieves methodically dismantled security measures one by one to gain access to the main underground vault, where they broke into more than 100 safe deposit boxes full of diamonds and other items. There were so many valuables inside they couldn't carry all of the loot with them.

"It was unbelief, really," said Antwerp police detective Patrick Peys. "It's unimaginable that something like that happens because the buildings are secured quite well."

The robbery occurred over a weekend, and when the diamond traders returned to work on Monday and learned there had been a robbery, there was pandemonium in the vault. "People were shouting, 'That's my box! That's mine!'" said Denise Oliver, who investigated the case for the insurance company representing most of the dealers. "People were crying, and people were fainting."

Treasure Two Stories Underground

The Diamond Center, a concrete office building in the heart of Antwerp's diamond district, is home to hundreds of diamond dealers, many of whom store their precious goods in a vault two stories underground.

Security in the three-block diamond district is tight. Guards patrol the narrow streets 24 hours a day, while giant metal barricades prevent unauthorized vehicles from entering or leaving the area. Multiple cameras track all movements.

Pedestrians are allowed to enter the area, but if they want to get into the 30 or so buildings they generally face state-of-the-art security measures. At some buildings, electronic photographs are taken of every visitor as they enter and exit, then transmitted to a central security office to be kept on file.

Without evidence of a break-in, police immediately considered the robbery an inside job. But who could pull off something on such a large scale?

Dealer With a Checkered Past

Police soon suspected one of the Diamond Center tenants, a one-time jeweler from Turin, Italy, named Leonardo Notarbartolo. He was known in his hometown as a family man who lived in the suburbs with his wife and children and did typical things, like playing soccer.

But Turin police knew of his criminal history, a long record of petty theft and small-time burglaries more than 20 years earlier. Police there suspect Notarbartolo is part of the "school of Turin" — criminals with legitimate jobs who come together for specific crimes. They believe he joined an all-star cast of criminals to pull off the Antwerp heist -- or possibly was the mastermind who brought the thieves together. Before the heist, Notarbartolo generally spent only about one day a month at the Diamond Center, making the trip to Belgium from Italy. But investigators soon learned that in the week before the robbery, he was at the Diamond Center every day.

"Every day, two, three times a day, he went down and did quite a good inspection of the whole area around the vault room," DeBruycker said.

A Spectacular Feat

The burglary went off without a hitch. According to the police reconstruction, this is what happened: At 7 p.m. Friday, the doors to the Diamond Center closed. Notarbartolo was one of the last people seen in the vault that night.

The next night, Saturday, at least three men took the elevator down to the vault some time around midnight. They or other members of the team had earlier disabled a motion detector that was supposed to protect the area, spraying silicone over the sensor, and had taped over a light detector. So the thieves were able to walk around freely. They went to a door next to the vault, broke in and reached for a small metal box, which they knew contained the key to the vault.

Police would not say how the thieves cracked the code to access the vault, but once they did and inserted their stolen key, they faced another even more intimidating obstacle: a last-resort alarm on the vault door.

Normally, when the 2-foot-thick metal door opens, two magnets are pulled apart triggering an alarm straight to the police. But the thieves cut the bolts holding the two magnets in place and taped the magnets together. Then, they moved the magnets to the side and opened the door. Because the magnets were still touching, the alarm never went off. "It was still active," Peys said. "It was still working, actually." The thieves were then standing inside the vault, but the diamonds were still in the safe deposit boxes. They assembled a special tool from common machine parts that allowed them to break the lock on each box. For the next four or five hours, police said, the burglars opened the boxes and went through the loot, throwing what they didn't want on the ground — a heap of extremely valuable jewels, watches, money. Police think they only left it behind because they couldn't carry any more.

As the thieves were leaving, police believe, they used a homemade key that gave them access to every door in the building. First they entered an office and stole the videotape recordings from the security cameras. Then, using the special key, they gained access to the building's underground garage, which had an exit opening onto a street outside the diamond district - just one block away from the metal barricades, the round-the-clock guards and the district's police station.

A Brilliant Plot, With Just One Flaw

Police believe that, before leaving town, the crew gathered at Notarbartolo's Antwerp apartment to divvy up the loot. That afternoon, they headed out of town. About 30 miles south of Antwerp, they pulled off the highway to a remote spot where no one could see them. This was where they made their first, and biggest, mistake.

Figuring they were safe in the woods, the group left behind bags of trash. But the man whose property they left it on routinely picks up litter, and he soon found the bags containing a glove, some documents, some money and diamond envelopes. Suspicious, he called the police. But the real break in the case was found in a smaller bag inside — a grocery store receipt, a half-eaten salami sandwich and an invoice, torn into pieces, for a shipment to the Diamond Center. Police pieced it back together and found it was a document referring to Notarbartolo. There also were toll booth receipts dated shortly before the robbery from a highway used to cross the Alps from Italy on the way to Antwerp, as well as cell phone numbers traceable to Notarbartolo and a receipt from a hardware store listing items the thieves left behind in the vault.

In addition, when the detectives checked Notarbartolo's own safe deposit box in the vault, they found it was one of the few that wasn't touched. And back at his Turin home, police say they found 17 diamonds sealed in plastic, which they say matched numbered certificates left behind in the vault in Antwerp.

A Suspect, But No Answers

The evidence mounted against their Notarbartolo, and police didn't have to wait long to nab him. On the following Friday, less than a week after the crime, he walked into the Diamond Center acting as if nothing was unusual. Building security called police.

Certain that they had nothing on him, Notarbartolo gave them his address in Antwerp, where detectives found his wife and friends packing a car to leave.

"About one minute and they were gone — would have been gone," said Detective Rob Dictus. "It was the second lucky shot."

Though nearly empty, the apartment yielded more evidence, including a small diamond found in a rug and a slab of salami and bottle of wine matching the receipt found in the woods.

Notarbartolo was arrested. He remains in jail in Antwerp, awaiting trial. Under Belgian law, the maximum penalty he can receive is five years or a few more if it's proven that organized crime was involved. His lawyer, Basili Foti, concedes there is evidence indicating Notarbartolo knows something about what happened, but told ABCNEWS, "There is always a minimum and a maximum penalty … we are looking for the minimum."

Police won't reveal what, if anything, Notarbartolo has said about the crime or his accomplices — or where the diamonds are.