The man died Friday night at a Washington hospital where he had been airlifted, Officer Araz Alali, a police spokesman, said.
The man poured the contents of a red canister of gasoline on himself in the center portion of the mall Friday afternoon. He then set himself on fire, with passing joggers taking off their shirts to help put out the flames. Police had said he was conscious and breathing at the scene, but he was airlifted to MedStar Washington Hospital Center with life-threatening injuries.
Police are investigating the man's possible motives. Lt. Pamela Smith of the U.S. Park Police said Friday she was not aware that he had carried any signs with him or had articulated a cause.
One witness, Katy Scheflen, said she did not hear the man say anything intelligible before he set himself on fire. But she said she did notice that another man with a tripod was standing nearby and had disappeared by the time the police had arrived. It was not immediately clear whether a recording exists.
"He appeared to be waiting for something to happen. After it happened, he was gone," Scheflen, a Justice Department lawyer, said Saturday of the man with the tripod.
"I can't say what the connection was between them or whether there was a connection," she added.
The fire occurred in a city with jangled nerves following a Sept. 16 mass shooting at the Washington Navy Yard that left 13 dead, including the gunman, and a high-speed car chase outside the U.S. Capitol on Thursday. The chase ended with a woman being shot dead by police with a young child in the car.