OSLO, Norway – Armed, masked thieves burst into the lightly guarded Munch Museum on Sunday and snatched a version of Edvard Munch’s Expressionist masterpiece, “The Scream” (1893), as well as “Madonna” (1893-4) from the walls as stunned visitors watched in shock. The thieves then fled by car.

It was the second time in a decade that a version of the iconic “Scream,” which depicts an anguished, opened mouthed figure grabbing the sides of its head, has been stolen from an Oslo museum.

The two or three thieves, wearing black masks, threatened an employee of the Munch Museum with a handgun before grabbing the paintings, easily snapping the wires that attached them to the wall, witnesses and the police told the Associated Press and local press.

“He was wearing a black face mask and something that looked like a gun to force a female security guard down on the floor,” one witness, Marketa Cajova, told the NTB news agency.

“What’s strange is that in this museum, there weren’t any means of protection for the paintings, no alarm bell,” a French radio producer, Francois Castang, who saw the theft told France Inter radio. “The paintings were simply attached by wire to the walls,” he said. “All you had to do is pull on the painting hard for the cord to break loose – which is what I saw one of the thieves doing.”

Police spokeswoman Hilde Walsoe told AP that no one was injured during the robbery and that police had found the escape car – an Audi A6 – and fragments of the paintings’ frames.

Munch made four versions of “The Scream,” which (like “Madonna”) was part of Munch’s “Frieze of Life” series, painted during 1893-94.

The Munch Museum had two of the “Scream” pictures; a private collector owns a third; and the fourth is on display at Oslo’s National Gallery. That version was stolen in February 1994 but recovered three months later.

Knut Forsberg, manager of Blomqvist Fine Arts, Norway’s oldest auction house since 1870,estimated the value of “The Scream” at between $59.6 million to $74.5 million. But he agreed it would be impossible to sell either painting on the open market because of their notoriety.

“Most likely, the thieves will demand a ransom to deliver the paintings back,” he said. Forsbert also refused to censure the museum for any lack of security. “You could fasten the picture better, but then the thieves would just cut the picture from the frame and damage the painting,” he said.

The “Scream,” stolen in 1994, is a work on paper. Police recovered the fragile work undamaged in a hotel in Asgardstrand, about 40 miles south of Oslo. At the time, investigators said the trio tried to ransom the painting, demanding $1 million from the government. It was never paid, and three Norwegians were later arrested.