Agents say the armed robbers painstakingly prepared for the job, using high-tech gizmos including a GPS tracker and a remote-controlled pepper-spray launcher to subdue the drivers.
Agents identified the alleged ringleader as Adalberto Perez, 46. He was arrested this week at his home in the Miami suburb of Opa-Locka, Florida, almost exactly a year after the March 2015 robbery in Wilson County, North Carolina. Two accomplices remain at large.
It appears the case was cracked when a friend of Perez came forward just a few months ago. According to an FBI affidavit unsealed in federal court this week, the friend said Perez spent about a year preparing for the heist.
The target: a routine shipment of gold bars aboard a tractor-trailer sent by Miami-based Republic Metals to a processing plant in Bridgewater, Massachusetts, that serves jewelry makers in the Boston area.
The FBI says that friend - now a confidential informant - said Perez bought a GPS tracking device online and had it mailed to the friend's address, without telling him what was in the package.
The affidavit doesn't say how Perez was able to gain access to the truck, if he had any relationship with the TransValue shipping company, or if the plot involved still more accomplices.
But the friend said "Perez said he placed this technology under the TransValue trailer in order to track its location," and that Perez also rigged a pepper-spray device inside the cab, the affidavit says.
TransValue chief executive officer Jay Rodriguez has said the truck left Miami about 4 a.m. that Sunday. The tractor-trailer appeared much like any other traveling up the East Coast. The drivers apparently had no idea they were being tracked by three armed robbers following them in a white van.
Shortly after dusk along a lonely stretch of I-95 in North Carolina, the truck's cab suddenly filled with pepper spray, launched by remote control, forcing its sickened drivers to pull over. The white van stopped on the highway shoulder as well.
At first claiming in Spanish that they were police officers, the men bound their hands with plastic ties and marched them into the woods. Then they put out orange traffic cones to make the stopped truck appear innocuous, and wore reflective clothing to appear as though they belonged on the roadside, too, according to the affidavit.
The thieves then cut off trailer's locks, quickly unloaded 275 pounds of gold and about 40 silver coins into the van, and sped off, leaving numerous drums of silver behind.
By the time the two drivers came out of the woods and flagged down passing motorists, the thieves were long gone.
After the robbery, the FBI informant said, Perez showed him one of the 26-pound gold bars at his home. He said he watched as Perez chipped away pieces to sell bit by bit, and used his cellphone to take photos of this gold and the tools Perez used.
The informant, identified as "CS" for confidential source, gave the images to the FBI; in one, the gold bar shows a distinctive Republic Metals stamp.
"Perez told CS he sold all of the gold he kept from the robbery," and used the money to buy three homes, three Nissan vehicles and a boat. He also had some gold fashioned into jewelry, some of it featuring religious icons, according to the FBI.
The informant said Perez gave him a gold bracelet, the FBI said.
After the friend came forward, investigators were able to use cellphone tower records to show that a phone linked to Perez traveled north through Florida along the same I-95 route as the truck that day. The FBI affidavit says the phone's last known location was in Dillon, South Carolina, where the truck refueled. The robbery took place an hour or so later.
Perez remained in jail without bail Friday on federal robbery and firearms charges, pending a Tuesday hearing.
"The complaint was quite an interesting read, but they are merely allegations," said his attorney, Frank Graviria, in an email. "We intend to fully investigate these serious allegations."
FBI spokesman Mike Leverock said additional suspects are being sought, and a $25,000 reward for information leading to an arrest and conviction still stands. The FBI distributed sketches of two other robbers based on information from witnesses.
Perez isn't the first man arrested in the case. Last year, Miguel Bover was sentenced to more than three years in federal prison after pleading guilty to an extortion charge, stemming from an attempt to sell one of the stolen bars. Bover, however, was not directly involved in the robbery itself, nor was the informant.
That bar is still the only one that has been recovered, but typically prosecutors will seek to seize property and assets of those involved to later sell and pay restitution to any victims.