NBC4 reporter Jackie Bensen tweeted that the incident "may involving [sic] camping stuff/belongings of a homeless person. Very strange." Yahoo's Chris Moody says police tell him the fire is out and that the man is alive and conscious. A medical helicopter is on the scene.
Update: The Washington Post reports that the man sustained "life-threatening injuries," according to a D.C. Fire Department spokesperson. There is no official word as to how the man caught on fire. "[H]ow it started, don’t know," said the spokesperson.
Update #2: Two men reportedly tamped out the flames with their shirts.
My mom was near the guy who lit himself on fire on the Mall. Says these guys put it out with their shirts pic.twitter.com/xJToYEurqI— Justin Sink (@JTSTheHill) October 4, 2013
Update #3: A witness tells the Associated Press that she saw the man dump a red canister of gasoline on his head before setting himself aflame.
Update #4: A helicopter airlifted the man to a hospital.