Today marks the 17th anniversary of Sept. 11, 2001, and Donald Trump seems... extremely pumped?

As the world remembers the thousands of people who lost their lives in the attack on the World Trade Center, President Trump flew to Johnstown, Pennsylvania with Melania this morning to attend a memorial event. But his perplexing facial expression and his choice to pump both fists in the air on the runway were an odd choice for such a solemn occasion.

WATCH: President Trump greets supporters upon arrival in Johnstown, Penn., while en route to Shanksville to honor those who died aboard United Airlines Flight 93 when it crashed 17 years ago today during the 9/11 attacks. https://t.co/TI1qXHQQNO pic.twitter.com/Uum9rmdV9j — NBC News (@NBCNews) September 11, 2018

The Trumps were on their way to a 9/11 Memorial Service in Shanksville, PA, and many people feel the tone-deaf gesture and strangely excited vibe the president gave off as he greeted assembled supporters was wildly inappropriate.

Twitter users, including Chrissy Teigen, were quick to scrutinize the photo, calling Trump out for his chipper and insensitive behavior on national day of mourning.

what a raging embarrassment https://t.co/d9V9OLCKJ6 — christine teigen (@chrissyteigen) September 11, 2018

I’ve never been as excited for anything as Trump is for 9/11 https://t.co/gmuuHuZFin — Jess Dweck (@TheDweck) September 11, 2018

He can’t even take 9/11 off from being a colossal schmuck... — andy lassner (@andylassner) September 11, 2018

Pumped to commemorate some deaths, y’all. https://t.co/UCWPEIEUyk — ana marie cox (@anamariecox) September 11, 2018

Trump fist-pumps as he arrives at a memorial service for victims of a violent attack https://t.co/9KeMlJUOfe — Aaron Rupar (@atrupar) September 11, 2018

It’s the anniversary of one of the worst tragedies in American history - and Donald Trump is PUMPED!! https://t.co/kLtcDQYZ4e — Rex Huppke (@RexHuppke) September 11, 2018

10 years after conservative media freaked out because the obamas did a fist bump at a 2008 rally, here's trump fist-pumping as he arrives at a 9/11 commemoration https://t.co/N5q52kIEcx — David Mack (@davidmackau) September 11, 2018

This man never, ever, ever fails to make clear to anyone paying a second of honest attention that something is seriously wrong with him. https://t.co/gDp8tYA2qL — Daniel Summers (@WFKARS) September 11, 2018

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? https://t.co/7zOTiz6N9e — Elizabeth West (@Limeylizzie) September 11, 2018

When I say 9, you say 11! 9! https://t.co/6T73Lr14lf — pourmecoffee (@pourmecoffee) September 11, 2018

Earlier this morning, Trump tweeted a simple "!7 years since September 11th" with an exclamation point.

17 years since September 11th! — Donald J. Trump (@realDonaldTrump) September 11, 2018

He also tweeted a message to Rudy Giuliani and a few thoughts on other, unrelated things, like collusion with Russia.

Rudy Giuliani did a GREAT job as Mayor of NYC during the period of September 11th. His leadership, bravery and skill must never be forgotten. Rudy is a TRUE WARRIOR! — Donald J. Trump (@realDonaldTrump) September 11, 2018

How hard is it to write a thoughtful message to the families of those lost in the attack, thank the first responders, encourage America, or at the very very least, not pump your fists?