The Scream is a compelling image–a distorted man stands on a bridge, mouth open wide. It's also one of the most familiar in Western art: It was mass-produced by the artist Edvard Munch, and the figure of the man has inspired numerous pop culture references. At least one neurobiologist even thinks we’re hard-wired to respond to the face, writes Kristy Puchko for Mental Floss. In fact, The Scream is so compelling that some art thieves were compelled to steal from the Munch Museum in Oslo, Norway, at gunpoint, on this day in 2004. And nobody knows why they did it.

The painting is “almost impossible to value,” New York art dealer Franck Giraud told The New York Times at the time of the theft. He estimated that “it could sell for over $100 million and become the most expensive painting in the world,” In 2012, this actually happened with a different version of the painting. But given the difficulty of reselling such a famous painting, the value alone can’t explain why art thieves might have stolen it. The painting might have been taken for ransom, Walter Gibbs and Carol Vogel wrote for the Times.

But it was hard to know, especially given the showy (and dangerous) manner in which the thieves took the painting and another famous Munch piece, Madonna. The museum was open and it was just after 11:00 a.m. when two robbers wearing balaclavas entered the museum and threatened museum guards, who weren’t armed, with pistols.

“Speaking in Norwegian, one of the men held the two guards at gunpoint, ordering them to the floor, while the other used a wire cutter to clip the framed paintings free of the wall,” Gibbs and Vogel wrote. “Witnesses described the thieves as clumsy, even dropping the paintings on the way out.”

The discovery later that day of the paintings’ frames and glass led art fans to fear the art had been damaged. But, two long years after the initial theft, the paintings were both recovered. Although some reports had suggested the paintings might have been destroyed, neither was very badly damaged–although, wrote Jonathan Jones for The Guardian in 2007, the damage the paintings did sustain “was caused by carelessness and neglect.”

The Scream and Madonna, he and others believe, were stolen to distract police from another investigation, one into a murdered Norwegian police officer. “This had not been a sophisticated crime,” the curator of the Munch Museum, Ingebørg Ydstie, told him. By the time the paintings were found, the perpetrators had already been identified, charged and found guilty of the theft of the paintings. Their motives remain mysterious to art fans, but they probably had little to do with the monetary value of the paintings.

It wasn’t the first time a version of the painting had been stolen–Munch did four versions in all, all confusingly titled The Scream. Two of them are finished paintings which belong to Norway, both of which have been stolen and recovered, while the other two–including the one that sold for almost $120 million in 2012–are pastel drawings.

In the 1994 theft, writes Puchko, “bandits placed a ladder up to the window of the National Gallery in Oslo, slunk inside, and made off with the other version of The Scream.” They left a note saying “Thanks for the poor security,” she writes. That time, the painting was back within three months. As Richard W. Stevenson reported for the Times, the story of its theft and recovery was equally mysterious and dramatic. There's just something about this painting.