President Donald Trump greeted supporters with a clenched jaw and double fist pumps as he arrived at a Pennsylvania airport for a 9/11 memorial service, prompting a social media backlash over what many said were inappropriate gestures for the weighty day.

The commander-in-chief can be seen in the photo with First Lady Melania Trump, as he’s raising both fists in the air and clenching his jaw. The president was on his way to pay respects for the fallen heroes of United Airlines Flight 93. The plane crashed as passengers and flight crew stopped a hijacking by a group of terrorists.

The picture was shared by reporters instantly, quickly went viral across social media as the president’s critics condemned his conduct.

“It’s the anniversary of one of the worst tragedies in American history – and Donald Trump is PUMPED!!” tweeted Chicago tribune columnist Rex Huppke.

Also, Trump first marked the 9/11 anniversary with a tweet about Russia and former Democratic presidential nominee Hillary Clinton before he sent a tweet regarding the attacks 17 years ago.

Trump has frequently been criticized for his behavior during serious events, particularly the September 11 attacks. On the day of the attack, Trump boasted on New York’s Channel 9 News that, after the towers collapsed, Trump Tower at 40 Wall Street was the tallest in Manhattan.

During his 2016 presidential campaign, Trump made the false claim thousands of Muslims in New Jersey were cheering the attacks after they heard the news.

Trump also has said that he went to Ground Zero to watch the clearing of the rubble and that he “helped a little bit,” a claim others have challenged.