On July 7, 2013, a Middle Eastern man boarded a flight from Los Angeles to Oakland. He was bearing a 4-carat diamond worth $175,000, as well as two smaller, 2-carat gems, intending to sell them in Oakland to a man he'd met over Craigslist. The buyer paid for his plane ticket and also a limo, which picked him up at the airport and drove him to a location in El Cerrito, Calif., just north of Oakland.

It was at this point that the man surely started to notice something was wrong. The limo was supposed to go to a bank—or maybe a jewelry appraiser, the specifics aren't clear—but the driver instead drove to the location in El Cerrito.

That's when three men came out of hiding, at least one of whom was armed with a gun.

We know these details because the man—who the thieves left pistol-whipped and bloodied—was not the first to be robbed in such a manner. According to a recently released federal search warrant, the gang had made 17 other such robberies or attempted robberies, all under the same modus operandi: They'd offer to buy high-priced jewelry over Craigslist, pay for the flight out to Oakland (occasionally with a stolen credit card), rent a limo, and then ambush the victim at some secluded location.

In one case, the gang stole a Cartier ladies watch worth $90,000 from a Portland, Ore., victim. In another, they flew in a 22- or 23-year-old woman from Pennsylvania before relieving her of a Gold Presidential Rolex—the second such watch they'd stolen. The first, strong-armed from an "older" victim from Denver, they sold for $19,000.

Just about every day, someone is robbed after answering a Craigslist ad. The goods are usually relatively inexpensive: an iPhone, a used car, a bicycle. But the case of the Oakland jewelry robbers may be the most ambitious, highly organized, and lucrative Craigslist caper yet.

And the gang's alleged mastermind orchestrated the whole thing from prison.

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Organized crime is migrating to the Internet, increasingly taking the face-to-face, back-alley meetups of Hollywood mafia out of the equation. Faceless, anonymous hackers steal credit card info from millions without ever needing to leave their bedrooms; shielded behind layers of anonymizing technology, drug dealers run marketplaces in hidden corners of the Internet, shipping a cornucopia of narcotics to customers they never meet and who pay in untraceable cryptocurrencies. The Oakland gang, however, is a reminder that traditional thieves are also using the Internet to find new and elaborate ways to relieve you of your valuables—in person.

The group's demise hardly began with a high-tech digital sting.

On June 20, a pair of police officers were on a stakeout in Oakland when they saw a stretch limo pull up nearby, hailed by a man on foot. The cops were there for a separate case, but they watched the limo closely as two more men approached, one brandishing a gun.

Either the passenger or the driver, who wasn't in on the robbery, figured out what was up. The car sped away. The three men, identified in court documents as Keegan Leecodi Cotton Jr., Jaedon Evans, and Rafael Davis, fled. But, pursued by the undercover cops, they didn't make it far. After looking into the men's cell phone records, investigators soon realized the female passenger, who'd flown in from Denver to sell a diamond, was hardly a unique victim.

And the suspects they already had in custody were only part of a larger, amorphous criminal enterprise, which stretched across the state of California.

It was in a small city 200 miles south of Oakland, in fact, where the FBI would catch its biggest break. By December, investigators had used cellphone records to track down one suspected conspirator to a cell at the California Men's Colony, a medium security prison in San Luis Obispo, where he was serving a seven-year sentence for a 2012 robbery conviction.  

A sweep of the man's cell uncovered a hidden, contraband phone, whose browser history was like a timeline of a scam in action. The phone's message inbox, too, was filled with incriminating conversations with other co-conspirators. The man has even occasionally called Craigslist sellers directly from his prison cell.

When they sat the prisoner down on Dec. 16 and confronted him, he was eager to cooperate. He'd made his son his criminal protege, who he'd "schooled"  on the "intricacies of criminal conspiracy," according to the affidavit. Now the younger man risked following his father's footsteps in other ways: The three men arrested in June had implicated him as a co-conspirator. So in a desperate bid to reduce his son's potential sentence, the inmate—identified in court documents as only a Confidential Human Source, or CHS—told agents everything.

That's how the FBI learned about 18 of the group's robberies, including the diamond and Rolex thefts. It's also how they managed to monitor one of the last outstanding members of the gang: Michael Anthony Martin, who went by the nickname Diesel and often set up the limo rides for the victims. Martin alternated between hiring an unsuspecting driver or using an accomplice. His preferred rental agency was Avis. 

Even after the June 20 arrest, Martin was still orchestrating robberies. One, in December, unknowingly put him in the middle of an FBI sting. Agents had identified a potential victim via phone records, then used an agent to pose as the woman. After getting in a limo procured by Martin at the Oakland airport, the agent quickly realized the driver wasn't an innocent professional. She was actually one of Martin's accomplices. The agent called off the sting for her own safety.

In January, with police listening in, the CHS called Martin to plan future thefts. Over the course of multiple conversations, Martin unknowingly implicated himself in many of the alleged crimes, including the violent attack on the owner of the $175,000 diamond. (For reasons that aren't made clear in the warrant, the thieves only made off with the two smaller gems.)

But the arrest in June had left him jumpy, Martin revealed. He told the CHS he was so worried the police were onto him that he "looked out the window every morning at 5:00, had a bag packed, an escape route, and a motorcycle without a tag," according to the affidavit.

Those precautions didn't help. Shortly after that conversation, police raided Martin's home in Tracy, Calif. There, they found a .38 caliber pistol, which he could not legally possess due to a 1998 robbery conviction.

Martin turned 40 years old on Feb. 3. He celebrated from inside a jail cell in Sacramento. It's not clear what will happen to the CHS, or his son. "The FBI has made no promises to the CHS," the search warrant affidavit makes sure to stress.

Photo via Kim Alaniz/Flickr