The solemn morning marking the 17th anniversary of one of America's darkest days was greeted with a series of angry tweets and double fist pump from President Donald Trump.
Critics condemned Trump on Tuesday for a "lack of respect" and an "inability to feel empathy for another person's loss" as he was photographed acknowledging supporters with a triumphant double fist pump as he arrived to a 9/11 memorial service in Pennsylvania.
The president, joined by first lady Melania Trump, took part in a somber remembrance in Shanksville, Pa., honoring the victims who were on board Flight 93 that fateful day.
A group of supporters met Trump as he arrived in Pennsylvania, prompting the president to smile before raising both fists and clenching his jaw in a celebratory gesture.
The double fist pump drew scorn form critics.
"He can't even take 9/11 off from being a colossal schmuck ... " tweeted Andrew Lassner, executive producer of "The Ellen Show."
Actress Elizabeth West was appalled by the act.
"Can you imagine having so little sense of decorum, sensitivity, self-awareness, that your first instinct upon arriving for an incredibly solemn ceremony, is to act as if you're at one of your rallies?" she wrote.
Trump was also photographed giving a thumbs-up as he toured the memorial to the 40 Flight 93 victims. The passengers and crew were killed when the plane crashed into a field as they were attempting to fight off the hijackers who had commandeered the aircraft. In all, nearly 3,000 people were killed on Sept. 11, 2001, when terrorists hijacked four commercial planes and flew them into the World Trade Center in Manhattan, the Pentagon and the Pennsylvania field.
In his speech, Trump remembered the "band of brave patriots" on Flight 93 who resisted hijackers and sent a message that the nation would "never, ever submit to tyranny."
He said the site marks the "moment when America fought back," and said the Sept. 11 anniversary recalls the day "a band of brave patriots turned the tide on our nation's enemies and joined the immortal ranks of American heroes."
Hours earlier, the president started the day much like any other, tweeting angrily about the ongoing Russia probe and other topics as mourners gathered to commemorate the worst terror attack on American soil.
He also sent out a series of tweets marking the date, praising his personal attorney Rudy Giuliani, who was New York's mayor at the time of the attack, and tweeting quotes from Fox News about the Russia probe and the Department of Justice.
While on his way to the memorial service, Trump was criticized for the tone of one of his tweets, which read: "17 years since September 11th!"
"This is not an exclamation point day. This is not a fist pump day. He sullies the solemnity of this day. History will not be kind to him. But WE will #NeverForget those who lost their lives and those who gave so much to help so many on that day, and the days that came after," responded Stephanie Tittle.
Trump has a long history of making controversial remarks about Sept. 11.
He often evokes the attacks while campaigning and has promoted a fake theory that thousands of Muslims in New Jersey were cheering the fall of the World Trade Center.
The native New Yorker has claimed he "lost hundreds of friends" and boasted that his appearances on TV have garnered more ratings than news coverage of the tragedy.
In an interview hours after the Twin Towers fell, Trump appeared to boast that the atrocity made one of his buildings the tallest in Lower Manhattan.
