The intergalactic lynx was in the midst of a miniature battle royale with Jack Skellington, of “The Nightmare Before Christmas” fame, inside the Prudential Center Mall on Friday night when it happened.

Steve, a 26-year-old Quincy resident who asked to be identified only by his first name, was wearing his “Furry” costume and charging up a “kamehameha,” an energy attack from the animated series “Dragon Ball Z.”

But before he released the blast, a white-haired man approached the staged fight.

“Only when he was kind of walking away did it kind of catch my eye, and I looked at my girlfriend, and she was also in costume, and she was like, ‘You know who that was, right?’ And I was like, ‘Was that Bernie Sanders?’” said Steve, who in the furry community goes by “Strobes.”

Apparently, it was.

“We were both kind of in disbelief,” Steve added.

An acquaintance who had been taking off-the-cuff photos of the faux fight between Strobes and Jack Skellington captured the moment.

One of the images, which went viral, shows Sanders smirking, his hands in his pockets, before he eventually veered to the left and around the playful commotion.

“He took like a quick glance and then kept going. He didn’t have a big reaction to it or anything,” said Steve, adding that he didn’t ask for a photo with Sanders because he was at first in a state of disbelief. “He kind of smiled — you can see him smiling a little bit in the picture.”

The Sanders sighting happened as the group mingled at the mall during the first night of Anime Boston, a popular annual event that draws thousands to the area decked out in creative get-ups inspired by characters from comic books, video games, and anime shows. The event is held at the Hynes Convention Center and Sheraton Boston Hotel.

A spokesperson for Sanders did not immediately return a request for comment about the senator’s encounter with the costumed revelers.

Sanders had been in Boston Friday for a series of sold-out events, including speaking at the Edward M. Kennedy Institute for the US Senate in Dorchester, promoting his book at MIT in Cambridge, and appearing with Sen. Elizabeth Warren at a rally in the Orpheum Theatre.

A second person also took a photo of Sanders as he walked through the hotel. In that picture, Sanders is mixed in with two people wearing white wigs.

Steve said part of him wished he had caught up to Sanders once he realized who it was, but he didn’t want to bother the elected official.

“He was soon out of sight and gone,” he said. “No one stopped him at all.”