During a speech at the Pentagon on the 18th anniversary Wednesday, Trump said he "vividly" remembers first hearing the news in 2001.
"I was sitting at home watching a major business television show early that morning. Jack Welch, the legendary head of General Electric, was about to be interviewed when all of the sudden they cut away. At first there were different reports. 'It was a boiler fire.' But I knew that boilers aren't at the top of a building. 'It was a kitchen explosion in Windows of the World.' Nobody really knew what happened. There was great confusion," the president said.
He went on to say his view of the attacks was shaped by more than just news coverage -- but what he saw with his own eyes.
"I was looking out from a building in midtown Manhattan directly at the World Trade Center when I saw a second plane, at a tremendous speed, go into the second tower," Trump said Wednesday.
Trump Tower is located on 5th Avenue between 56th and 57th Streets, a little more than four miles away from ground zero.
"Soon after, I went down to ground zero with men who worked for me to try to help in any little way that we could. We were not alone. So many others were scattered around trying to do the same, they were all trying to help," he said Wednesday.
Trump has previously spoken more generally about his whereabouts on the morning of the attacks.
During a campaign stop in Columbus, Ohio, in November 2015, Trump also said he was in his Manhattan apartment, but he went further Wednesday and said he could see people jumping from the towers.
"I have a window in my apartment that specifically was aimed at the World Trade Center, because of the beauty of the whole downtown Manhattan. And I watched as people jumped, and I watched the second plane come in," he said then. "Many people jumped, and I witnessed that. I watched that."
There is footage of Trump doing a video interview with a German news station near ground zero two days after the attacks.
"I've never seen anything like it -- the devastation, the human life that's been just wasted for no reason whatsoever. It is a terrible scene. It's a terrible sight. But New Yorkers are very strong and resilient, and they'll rebuild quickly," he said in that 2001 interview.
While Trump didn’t specifically say in his speech at the Pentagon when he went to the area near ground zero “soon after” the attacks, there is a widely circulated picture of Trump, wearing his go-to suit and a red tie, outside the New York Stock Exchange on Sept. 18, 2001.
Trump also recalled his time near ground zero during the reauthorization of the Victims Compensation bill in July at the White House.
At the time, he noted "many of those affected were firefighters, police officers, and other first responders," and then claimed, "and I was down there also, but I’m not considering myself a first responder. But I was down there. I spent a lot of time down there with you."