A couple visiting a street art exhibition at a mall in Seoul unknowingly vandalized an abstract painting by American artist JonOne, said to be worth $500,000, painting three large dark splotches across its surface.

The couple were confused by the array of brushes and paint tubes scattered on the ground beneath the canvas. They were meant to reflect the creative process of the artist, but the unwitting pair mistook the display for an invitation to add to the work.

“They thought they were allowed to do that as participatory art and made a mistake,” Kang Wook, CEO of Contents Creator of Culture, co-organizer of the exhibition, told Reuters. “We are currently in discussions with the artist about whether to restore it.”

A CCTV camera captured the young couple putting paint on the piece, which is currently on view in “Street Noise,” an exhibition at P/O/S/T, a gallery at Seoul’s Lotte Street Mall.

Half an hour after the incident, mall cops took the couple into custody. The gallery has opted not to press charges because it was an honest mistake.

JonOne, born John Andrew Perello, is a street artist known for his Abstract Expressionist-style graffiti. He painted the untitled piece, which measures nearly 23 by nine feet, in front of a live audience at a graffiti art show, “The Great Graffiti,” at the Seoul Arts Center in 2016.

The art supplies littered at the base of the work are said to be the very same paints and brushes he used to complete the work, and are considered part of the piece.

The artist’s auction record is €160,900 ($214,048), set at Artcurial in Paris for a painted car titled Rolls Royce modèle Corniche in 2013, according to the Artnet Price Database.

US graffiti artist JonOne (John Andrew Perello). Photo by Patricia De Melo Moreira/AFP via Getty Images.

The artist did not respond to a request for comment, but the gallery told the Korea Times that the couple may have to compensate him for restoration costs.

The vandalized artwork remains on view—but with an additional wire barrier and a new sign warning viewers “Do Not Touch.”

“Street Noise” is on view at P/O/S/T, Lotte World Mall, B1, 300 Olympic-ro, Songpa-gu, Seoul, February 26–June 13, 2021.