Guilty-stricken: Rick Abath, pictured above as police found him, has spoken about his involvement in the 1990 heist from a Boston art gallery . The security guard who was duped into letting the thieves at the center of America's most notorious unsolved art crime into the Boston gallery from which they looted paintings worth $500million has spoken of his guilt. Rick Abath, who was a college drop-out working night shifts at the Isabella Stewart Gardner Museum in 1990, said he still feels 'horrible' about his inadvertent role in the crime, which has baffled investigators for decades. Abath was duped by two thieves in police uniform, who persuaded him to let them into the gallery, then overwhelmed him and left him in the basement covered in duct tape. He spent the next seven hours handcuffed to an electrical box alongside another guard, while the two men cut loose enormously valuable Old Masters from their frames, including works by Rembrandt, Vermeer, Degas and Manet. The FBI has never come close to finding the paintings - despite supposedly promising leads last May - and there remains a $5million reward for information leading to their return. Abath reflected on the night of March 18, 1990, in an interview published by NPR. He said: 'They had hats, badges, they looked like cops, and I let them in...' 'Ultimately I'm the one who made the decision to buzz them in. 'It's the kind of thing most people don't have to learn to cope with. It's like doing penance. It's always there. He added: 'I don't want to be remembered for this alone. I'd like to be remembered for the good things I've done. I'm a husband, a father of two really cool kids. Scroll down for video . Scene: A security guard at Boston's Isabella Stewart Gardner museum stands outside the room from which most of the paintings were pilfered . Dutch Master: The thieves stole two Rembrandts . -  'The Storm on the Sea of Galilee,' left, believed to be the only . seascape the master painted, and 'A Lady and Gentleman in Black,' right . Irreplaceable: Chez Tortoni, painted by Manet, shows a man wearing a top hat at a jaunty angle; it was one of the last paintings to be stolen from the museum . 'Dressed as cops': This FBI sketch shows a likeness of the two men, who have never been caught . 'But they're saying it's half a billion worth of artwork.' In total the haul including three Rembrandt works, five sketches by Degas, a Manet painting and a painting by Vermeer - one of only 36 in the world. A bronze eagle statue, a Chinese beaker from 1100 BC and a painting by Govaert Flinck were also taken. Aside from two sketches of mustachioed men in police hats - one with glasses and one without - little detail has ever been given as to who the men may have been. Missing: The Gardner museum continues to display empty frames in the spots where the paintings should be . A petty Boston criminal, who had broken into the gallery before denies having anything to do with the heist, has since said he believes his boasts to criminal associates may have sparked the crime. Louis Royce, who was a teenager in the 1980s and made it inside the gallery, told veteran crime reporter Stephen Kurkjian that he believes information he gave 'criminal associates' about the lax security may have focused the thieves' attention on the Gardner Museum. According to Kurkjian, whose recently-published book about the heist was previewed in the Washington Post, the information passed up the chain in the criminal underworld until a Boston gangster decided to make the attempt. The FBI has periodically renewed its appeal for information about the artworks, and carries information about the reward prominently on its website. Reward: The FBI has claimed to be hot on the trail of the paintings in the past - but little has emerged. Pictured above is a 2013 press conference at which a $5million reward was announced . In 2013, the bureau claimed to have made 'significant investigative progress' after figuring out that the stolen paintings had been taken to Connecticut and Philadelphia. Agents also said 'a criminal organization with a base in the Mid-Atlantic states' was responsible, and had attempted to sell the paintings in 2003. Federal prosecutors have said they would even consider immunity for those who help recover the artworks, and said they could pay the huge reward anonymously. In May 2014, the bureau made another announcement, saying there had been 'confirmed sightings' of the work - and even naming three men in connection with the crime. However, two of them, Carmello Merlino, Robert Guarente, are dead, and the third, Robert Gentile, denies any involvement. Gentile has denied any knowledge of the missing work. In a long piece in the Boston Globe, Gentile, a long-time criminal in his 70s who recently got out of prison, revealed that FBI agents had raided his shed hoping to find the paintings. There was nothing there, and Gentile continues to deny he ever had anything to do with the theft. The museum, meanwhile, has been displaying empty frames in place of the missing masterworks ever since the theft. It is now offering virtual tours and lectures about the work, in an effort to make up for their continued absence - though the museum's directors continue to hold out hope they will one day return. Rembrandt, 'The Storm on the Sea of Galilee,' 1633 . Rembrandt, 'A Lady and Gentleman in Black,' 1633 . Rembrandt, 'Self-Portrait,' ca. 1634 . Vermeer, 'The Concert,' 1658–1660 . Manet, 'Chez Tortoni,' 1878–1880 . 'Ku' Chinese Bronze Beaker, 1200–1100 BC . Degas, 'La Sortie de Pesage,' date unknown . Degas, 'Cortège aux Environs de Florence,' date unknown . Degas, 'Program for an Artistic Soirée, Study,'1884 . Degas, 'Program for an Artistic Soirée,' 1884 . Degas, 'Three Mounted Jockeys,' date unkown . Finial in the form of an eagle, French, 1813–1814 . Govaert Flinck, 'Landscape with an Obelisk,' 1638 .
Rick Abath was college drop-out working night shifts at Boston's Stewart Isabella Gardner Museum in 1990 . Was fooled by thieves dressed as police, who tied him up in the basement . They then stole works by Rembrandt, Vermeer, Degas and Manet . Half-a-billion heist remains unsolved, and FBI has never even come close . Gardner museum continues to display empty frames, and is offering $5million reward for the return of the works .