A strange thing happened during an otherwise normal hearing on Capitol Hill this morning. During Treasury Secretary nominee Jack Lew’s Senate confirmation hearing, several members of the audience donned Robin Hood hats, then continued to quietly sit and watch the hearing.

The move had some viewers confused. One tweeted, “Uniformed Capitol Hill police now in Lew hearing room. Worried about possible protests. Keeping an eye on the folks in Peter Pan hats.”

“Pair of people seated at hearing just put on Peter Pan hats. Buckle up for possible protests…,” another said.

The hats were actually to promote a “Robin Hood Tax,” advocated by a group of the same name. The group describes the tax as “a small tax on Wall Street trading that has the power to raise hundreds of billions every year to help in the US, and around the world.”

Robin Hood Tax tweeted pictures of a hat-wearing audience member peeking out from behind Lew during the hearing, as well as plugging its tax proposal.

“Robin Hood is not amused with all this talk of lower corp taxes, #JackLew. We need Robin Hood, #RHT,” the group said.