NEW YORK—New York City police arrested on Saturday a man who they say is the anonymous artist Poster Boy, known for cutting up subway ads and re-pasting them to form collages with an anti-establishment message. Henry Matyjewicz, a 27-year-old living in Bushwick, Brooklyn, was taken by officers at an art event in SoHo and charged with two misdemeanor counts of criminal mischief, reports the New York Times.

The police say they were tipped off by someone who had seen the name Poster Boy on a flier for the event.

A man identifying himself as "Henry," however, called the Times on Tuesday in response to messages for Poster Boy sent through his friends, and cast what the paper calls "existential doubt" on whether Matyjewicz is, in fact, the anonymous artist.

"Henry is one of many individuals who believe in the Poster Boy 'movement,'" the man wrote in an e-mail message. "Henry's part is to do legal artwork while propagating the ideas behind Poster Boy. That's why it was O.K. for him to take the fall the other night. Henry Matyjewicz is innocent."

The Saturday night SoHo art event was a benefit for Friends We Love, a New York documentary video series that profiles young artists (a video of Poster Boy at work in the subway can found on their Web site). Moni Pineda, co-creator and producer for the series, said that police officers entered without showing a warrant and took away someone who she would only identify as "a friend."

"Poster Boy can be anybody," she added.

Pineda and others managed to post bail for their friend, but not before he had been transferred to Rikers Island. He was released early Monday morning.

"Socially, I'd like people to understand that there is a difference between what is right and what is just," Poster Boy himself wrote to the Times, the paper said, in answer to a series of a e-mailed questions. "If there is a law that is outdated, impractical, and/or immoral, people should have the right to challenge it. Remember, slavery was considered legal at one point. I consider the world's current modus operandi a modern slave system. I intend to challenge it in any way I can."