WASHINGTON (AP) - A man who set himself on fire on the National Mall in the nation's capital has died of his injuries, District of Columbia police said Saturday. Officer Araz Alali, a police spokesman, said the man died Friday night at a Washington hospital. The man's name and age were not immediately known, and his burns were so severe that authorities will need to use DNA and dental records to identify him, Alali said. The man poured a can 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 douse the flames. Police had said he was conscious and breathing at the scene, but he was airlifted to MedStar Washington Hospital Center. Police are investigating the man's possible motives. Lt. Pamela Smith of the U.S. Park said she was unaware that he carried any signs or had articulated a cause. One witness, Katy Scheflen, said that she saw a tripod set up near the man but that she did not hear him say anything intelligible before he set himself on fire. But it was unclear if the man was filming the incident. The immolation occurred in a city with jangled nerves following a Sept. 16 mass shooting at the Washington Navy Yard and high-speed car chase outside the U.S. Capitol on Thursday that ended with a woman being shot dead by police with a young child in the car.