Moments after the artist Banksy’s “Balloon Girl” painting sold at Sotheby’s Auction House on Friday, October 5, 2018 in London, a paper shredder hidden in the frame activated and carved half of the work — but not all of it, curiously — that had just gone for $1,367,471.83. On Saturday, the still-anonymous artist released a video showing how he did it.

The new video shows the assumed artist’s hands placing blades along the inside of a picture frame, with the sound of a buzz saw in the background. “A few years ago I secretly built a shredding into a painting, in case it was ever put up for auction,” reads a title card before the video shows gleaming blades being surreptitiously placed into the back of the frame.

The video shows dozens of blades being placed inside the frame.

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As the video shows, the shredder only appears to cut half of the painting into ribbons, leaving the little red heart balloon intact. It wasn’t immediately clear if the half-shred was intentional or a malfunction. “It appears we just got Banksy-ed,” Sotheby’s senior director Alex Branczik said in a statement that described the incident as “the first time in auction history that a work of art automatically shredded itself after coming under the hammer.”

“Balloon Girl” originally appeared in 2002 as a graffiti work in the United Kingdom. A version of the work was auctioned off in 2007 as well, and it’s one of the artist’s most recognizable works and was repurposed to support the Syrian people caught in the middle of a civil war in 2014. The auction price was the highest-ever for a Bansky work.

Despite the shredded work, Sotheby’s told the press on Friday they were in conversation with the winning bidder about what to do next. One art world observer says the work’s value would likely increase, despite it being sliced up. “Given the media attention this stunt has received, the lucky buyer would see a great return on the £1.02M they paid last night,” Joey Syer of MyArtBroker.com told the media Saturday. “This is now part of Art History in its shredded state and we’d estimate Banksy has added at a minimum 50 percent to it’s value, possibly as high as being worth £2m+.”

“The urge to destroy is also a creative urge,” is a quote by the artist Mikhail Bakunin, but in an Instagram video shared by Banksy along with the video, the artist misattributes it to Picasso.