President Trump on Tuesday began his day—on the 17th anniversary of the Sept. 11, 2001, terror attacks—by tweeting a defense of himself in the Russia investigation. A few minutes later, he retweeted a post about the worst terror attacks in U.S. history, adding #NeverForget #September11th. Nearly an hour later, he posted an inappropriately punctuated remembrance, tweeting “17 years since September 11th!” Trump will attend a ceremony in western Pennsylvania to honor the victims of the tragedy. More than 3,000 people were killed in the coordinated attacks after hijackers flew airplanes into the Pentagon and World Trade Center. A fourth hijacking attempt was stopped when 40 passengers and crew aboard United Airlines Flight 93 charged into the cockpit and intervened in the plot, which some believe was meant to strike the U.S. Capitol building or the White House. That plane crashed in Shanksville, Pennsylvania, where the 93-foot Tower of Voices memorial was dedicated on Sunday.