When the employees of a large warehouse outside Hartford, Connecticut arrived at work, they found a ladder on the side of the building, leading to a hole cut in the roof, discarded tools and an alarm system that appeared to need a battery.

Also missing were 40 pallets of brand name Eli Lilly drugs—valued at a whopping $60 million.

The largest heist in Connecticut history took place during a severe nor’easter overnight March 13, 2010—and the culprits, known as the Cuban Mob, had a days-long head start. But investigative work by the Federal Bureau of Investigation, the Bureau of Alcohol, Tobacco, Firearms and Explosives, and local cops tracked down the five culprits—and a cross-country string of cargo robberies totaling $100 million in merchandise.

All five involved in the scheme are now behind bars, the latest being one of the ringleaders who was sentenced to more than seven years in prison in December.

But detectives had a cold start to their pursuit of the thieves, after the storm that March morning.

The crime scene in Enfield, Connecticut quickly showed local cops, and the FBI agents who were called in, that those responsible had been prepared—and organized. A ladder had been stashed at the rear parking lot of the warehouse. The burglars checked for security guards, then went inside the property, using the ladder to access the top of the building. They cut a hole in the roof, lowered themselves inside and quickly disarmed the alarm system.

“They knew exactly how that type of alarm system was set up,” said Damian Platosh, FBI special agent at the New Haven field office.

To outside monitoring, it appeared simply as if the severe storm—which boasted 70 mph winds—had knocked out power to the warehouse.

The burglars backed in a tractor trailer and loaded up the exact number of pallets they could fit in the truck—the 40 shrink-wrapped loads of Zyprexa, Cymbalta, Prozac, Gemzar and other premium drugs.

“They took the cream of the crop, and they loaded the exact number of pallets that would fit into the trailer,” said Platosh. “They knew exactly what they were doing.”

The tools left at the scene were carefully examined. An FBI investigation determined that the exact grouping of those tools was purchased the night before at a major hardware store in Flushing Meadows, New York. (Federal “hot watch orders” have reportedly allowed targeted tracking of credit card purchases for nearly a decade.)

A plastic water bottle was also found at the Enfield scene. DNA traces on the bottle were matched to a Cuban national living in Florida—who also happened to have a criminal history of cargo theft.

As news of the huge theft spread, an anonymous call was also placed to Enfield local police. The tipster said only that the culprits had Cuban names, and one of them was known as El Gato (“The Cat”).

The Connecticut FBI agents reached out to the cargo theft experts in the agency—and were directed to the Miami field office and their cargo theft task force. The agents there suggested that a “follow car” had probably been used—and the burglars would have headed directly south perhaps 300 miles before stopping to rest far away from the scene of the heist.

Platosh said the resulting investigation was “classic gumshoe work”—checking the maps, contacting hotels, car rentals, airlines and even cellphone towers for various clues.

They identified the follow car and where it had been rented. That, coupled with surveillance footage, and the DNA lead from the water bottle, identified four suspects: Amed Villa, Amaury Villa, Yosmany Nunez and Alexander Marquez.

They located the drugs stash in self-storage units in Florida. But agents didn’t immediately move in. Instead, they put the units under surveillance—and used the time they figured they had before the pallets were sold to investigate the suspects’ other possible heists.

Eighteen months after the Connecticut theft, the self-storage units were raided. The four men were charged with four other multimillion-dollar thefts from warehouses. That included: a $13.3 pharmaceutical theft from GlaxoSmithKline in Virginia in 2009, $8 million in cigarettes and a cargo trailer from Illinois in 2010, $7.8 million in cellphones and tablets from a Florida location in 2011 and $1.5 million worth of cigarettes from a Kentucky facility in 2011.

The modus operandi was similar in each heist, with roof access, disabling alarms and making away with the goods in a tractor trailer. Amed Villa was connected to four of the five scenes through DNA he left behind on discarded objects, according to federal authorities.

“This investigation started in Connecticut and branched out around the country,” said Platosh.

Amed Villa, a 51-year-old Cuban national, was sentenced to seven years in prison in December after pleading guilty to multiple counts of theft. Amaury Villa, Nunez and Marquez have also been sentenced to stints in federal prison. A fifth conspirator, Rafael Lopez, who helped purchase the burglary tools in New York, was sentenced to more than six years in prison for his role in the scheme, in 2014.