President Biden briefly donned a “Trump 2024” hat during a visit to a Shanksville, Pa., fire station in what the White House said was intended as a show of unity on the anniversary of the 9/11 attacks.

“At the Shanksville Fire Station, @POTUS spoke about the country’s bipartisan unity after 9/11 and said we needed to get back to that,” White House senior deputy press secretary Andrew Bates posted on the social platform X. “As a gesture, he gave a hat to a Trump supporter who then said that in the same spirit, POTUS should put on his Trump cap. He briefly wore it.”

Biden put on the hat during a meeting with community members that was closed to the press. A photo and brief video of the moment quickly went viral among Republicans, including some who used it to attack Biden’s mental sharpness and his support for Vice President Harris.

“BREAKING: Kamala did so bad in last night’s debate, Joe Biden just put on a Trump hat,” the Trump campaign’s rapid reaction team posted on X.

“Thanks for the support, Joe!” the campaign added in a separate post.

“What’s Happening?” senior Trump campaign adviser Chris LaCivita posted along with the photo.

Biden has spoken often about trying to unite the country and lower the political temperature, even as he has aggressively attacked his predecessor as a threat to democracy. Biden ended his reelection bid in late July and has since been replaced by Vice President Harris, who is locked in a neck and neck race with Trump.

Biden, Harris, Trump and GOP vice presidential nominee Sen. JD Vance (R-Ohio) all attended a 9/11 memorial event in New York City on Wednesday morning. Biden and Harris visited Shanksville to honor the victims of Flight 93, and Trump made a stop there later in the day.