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Was Banksy at the evening sale at Sotheby’s on Friday night? That was the question on everyone’s lips when one of the Bristolian street artist’s paintings mysteriously self-destructed as the contemporary auction drew to a close.

Girl with a Balloon (2006) was the final lot of the night, and just as the canvas hammered at £860,000, or £1.04m with fees—just above his auction record in pounds achieved in 2008—an alarm was triggered inside the work of art. Onlookers turned just in time to see the canvas slip through its faux-gilt frame and be shredded into pieces.

“It appears we just got Banksy-ed,” said Alex Branczik, the auction house’s head of contemporary art, Europe, immediately after the sale. “He is arguably the greatest British street artist, and tonight we saw a little piece of Banksy genius,” he said, adding that he was “not in on the ruse”, although it is not clear whether other members of staff were. Some commented on the unusually thick frame, which could have easily concealed a shredding mechanism.

After a man dressed in black sporting sunglasses and a hat was seen scuffling with security guards near the entrance to Sotheby’s shortly after the incident, speculation mounted that the elusive artist had himself pressed the button that destroyed the work. According to the provenance, Girl with a Balloon was acquired directly from the artist in 2006.

“We are busy figuring out what this means in an auction context,” Branczik said. “The shredding is now part of the integral art work. We have not experienced a situation where a painting has spontaneously shredded, upon achieving a record for the artist.”

One potential outcome, according to a spokeswoman, is that the destroyed painting could be preserved as a document of the guerrilla tactic. “You could argue that the work is now more valuable,” Branczik said. “It’s certainly the first piece to be spontaneously shredded as an auction ends.”