Hillary Clinton left a service at the 9/11 memorial on Sunday early.
According to a statement from Clinton's campaign spokesperson, Nick Merrill, the candidate felt "overheated," so she went to her daughter's apartment. Clinton is "feeling much better," the statement said.
That statement came more than an hour after reporters following the campaign tweeted about the incident, saying the 68-year-old left without her press pool. Her whereabouts at the time were unknown, but it was later confirmed that she had retreated to her daughter's nearby apartment.
She is overcoming pneumonia and was diagnosed with it Friday, her doctor said.
Video taken at the scene and posted on social media shows Clinton being held up by three people. She staggers and appears to trip on a curb as they help her into a vehicle.
"I take two pictures before she passed me. She looked like everything was fine and everything was good," the man who filmed the video, Clinton supporter and Czechoslovakian immigrant Zdenek Gazda, 50, told Buzzfeed News. "I just saw the secretary waiting for the van, and the van came, and she (couldn't) walk inside, and she (got) helped. She lost her shoe and everything."
The incident comes as Donald Trump has questioned whether she is healthy enough to serve as president. Clinton, who emerged saying, "I'm feeling great," has said she is healthy and fit to be president.
After the incident Sunday, she told reporters, "It's a beautiful day in New York."
Read more at Buzzfeed News.
The Associated Press contributed to this story.