New developments in the infamous Isabella Stewart Gardner Museum heist case have led the FBI to believe they have zeroed in on the thief. After 23 years, the 13 missing masterpieces, some painted by the likes of renowned artists Rembrandt, Degas, Vermeer, and Manet could finally return to their missing frames which still hang sullenly on display in the Fenway-area gallery.

Recently, WGBH’s Emily Rooney spoke with Gardner Museum director Anne Hawley and FBI special agent as well as art crime unit investigator Jeff Kelley to find out where exactly the Bureau stands in terms of catching the culprit and how the robbery subsequently affected the Museum years after it took place.

First, a quick rundown of how two men pulled of the largest, most expensive private theft in the history of the game. On St. Patricks Day in 1990, two men dresses up as police officers. They buzzed the building and were allowed entry with no questions asked. They were then able to coerce one of just two security guards on duty to come out from behind the desk where a police alarm was situated and handcuff him. When the second security guard made his way down, he too was cuffed.

Unable to remove many of the frameworks bolted to the wall, the thieves proceeded to cut many of the works from their frames. Interestingly, they passed by works by Italian Renaissance geniuses Raphael and Botticelli. Their entire load was estimated at $500 million. FBI is offering a $5 million reward.

In speaking with Emily Rooney, Kelley said of his knowledge of the assailant(s) and refusal to publicly identify him/them, “we feel it is important to kind of lay our cards out on the table and say we know who did it, and we know who is involved, but we need your help. We still have an investigation here, and we still have to preserve the integrity of the investigation.”

But also in need of preservation, at least directly after the robbery and possibly since, is museum safety. Hawley noted that the Gardner Museum was plagued with bomb threats, extortion attempts, multiple evacuation precautions due to criminals hoping to take advantage of the museum’s weakened state.

But as the FBI continues its undisclosed advances, it’s calling on the masses for help. The Bureau recently released a slew of ‘Most Wanted’ posters for each stolen piece, a move WGBH notes strikingly resembles what the FBI did just prior to capturing notorious gangster Whitey Bulger.

Check out Emily Rooney’s interview with FBI agent Jeff Kelley here: