Transcript for Artist Banksy pulls million-dollar prank

New details about the shocking prank at a London auction house. Just after a painting by banksy sold for $1.4 million, half of it slipped through a shredder in the frame. Tonight, banksy has revealed some clues about how and why it happened. Here's Zachary kiesch. Reporter: Tonight, the setup that that shook up the art world. The British graffiti artist banksy is known as a conversation starter. But all the chatter tonight is about his gallery painting of the iconic "Girl with balloon." The artwork sold at sotheby's in London for a reported $1.4 million. But seconds after the sale, this happened. First, the beeping of an alarm. And then, the mounted canvas disappears and emerges from the bottom of the frame, shredded. The auction house, caught off-guard by the stunt, scrambled. Saying online, "It appears we just got banksy-ed." The elusive street artist, who has never revealed his identity, seemed to relish the buzz. Hours later, revealing how he pulled it off. Saying, "A few years ago, I secretly built a shredder into a painting in case it was ever put up for auction." Some experts say the move will make him money. That stunt, I think, has added a minimum of $5 million to his back pocket. Reporter: Tom, banksy's popularity has spread around the world by using his paint brush as a tool to address social injustices inside the world of art and beyond.

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