The man, identified Thursday as Arnav Gupta of Bethesda, Maryland, died of his injuries later Wednesday after being transported to a local hospital, U.S. park police said.
The Ellipse is a 52-acre park area that lies south of the White House and north of the National Mall, in the heart of Washington. The fire occurred just north of the Washington Monument.
Secret Service spokesman Jeffrey Adams said in a statement Wednesday that the agency's Uniformed Division Officers "responded in seconds" after the "male individual lit himself on fire." Officers then began administering first aid to the man.
"The individual is being transported to a local hospital," Adams added.
A spokesman for the Washington Fire Department told CNBC that, "I can confirm that we've transported one patient with burns from the Ellipse and we're now on the scene assisting law enforcement," referring to Park Police and U.S. Secret Service officers.
Several outlets reported that the man's injuries were life-threatening.
Alina Berzins, a 17-year-old recent high school graduate from Lorton, Virginia, told CNBC that she was visiting the National Mall with two of her cousins from Bolivia when "we saw this man" on the Ellipse and "he starts running, and then we saw him covered in flames."
"He started to walk" and then "cops started coming to the area and he collapsed," Berzins said. The fire then was extinguished, she said.
Berzins said that she and the other passersby in the area were stunned by the sight of the man.
"Everybody was in shock," Berzins said. "I was in shock."
Berzins' father posted on Twitter a video that his daughter took of the incident.
She said that several dozen law-enforcement officers flooded the scene and were joined by a helicopter overhead and multiple Fire Department vehicles.
A White House spokesman had no immediate comment.
The man's motive for setting himself on fire remains unclear.
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