“Donald Trump has been lying about 9/11 since 9/11,” O’Donnell said on Monday night. “Here is Donald Trump’s most vile lie about 9/11.”

He played a clip of Trump claiming during a Republican debate that he “lost hundreds of friends” on 9/11.

O’Donnell said it was a lie ― and noted that he called Trump out over it at the time.

Trump during a subsequent appearance altered it to losing “many, many friends,” but O’Donnell said that was a lie too.

“Donald Trump lost zero friends on 9/11,” he said. “Donald Trump attended zero funerals of 9/11 victims. Zero. But Donald Trump tried to steal the grief of all of the families who lost someone on 9/11.”

O’Donnell noted that United Airlines Flight 93 was potentially headed for the U.S. Capitol on that morning, but instead crashed in a Pennsylvania field after the passengers revolted.

Then, he played footage of January 6 attackers breaking into the Capitol just steps away from a plaque honouring those aboard that flight for stopping the attack.

“In the 21st century, only two groups have tried to attack the United States Capitol: al-Qaida, led by Osama bin Laden, and Trump supporters, led by Donald Trump,” he said. “Only the Trump attackers actually did damage to the Capitol.”

See more from his Monday night broadcast: