Unsolved Boston Art Heist

From here:

BOSTON – It remains the most tantalizing art heist mystery in the world.

In the early hours of March 18, 1990, two thieves walked into Boston's elegant Isabella Stewart Gardner Museum disguised as police officers and bound and gagged two guards using handcuffs and duct tape. For the next 81 minutes, they sauntered around the ornate galleries, removing masterworks including those by Rembrandt, Vermeer, Degas and Manet, cutting some of the largest pieces from their frames.

By the time they disappeared, they would be credited with the largest art theft in history, making off with upward of a half-billion dollars in loot far too hot to sell.

Now, 20 years later, investigators are making a renewed push to recover the paintings. The FBI has resubmitted DNA samples for updated testing, the museum is publicizing its $5 million, no-questions-asked reward, and the U.S. attorney's office is offering immunity.

Two billboards on Interstates 93 and 495 are also advertising the reward.

"Our priority is to get the paintings back," U.S. Attorney Carmen Ortiz said. "If someone had information or had possession of the paintings, immunity from prosecution is negotiable."

Investigators say they've largely ruled out some of the more popular theories, from the specter of a recluse billionaire art collector to the hand of notorious Boston gangster Whitey Bulger.

More likely, investigators say, the two were homegrown thieves with knowledge of the museum's security system — including the absence of a dead man's switch that would have alerted police once the guards became incapacitated. They might have even underestimated the breathtaking scope of their crime.