The victim, identified as Prapan Phromwisit, drove from Sam Yan market, followed a motorcycle to the flyover without seeing any sign that the bridge was closed.
He said the motorcycle has abruptly u-turn because there were barricades and fence. Mr Prapan stopped his car and tried to notify other cars that followed him that the bridge was closed.
At that time, there were three gunshots from the barricade, hitting his car windows and slightly hit his ear. He then drove away from the bridge to hospital.
A woman was reportedly shot in the leg.
In the latest development of the anti-government rallies, the protesters plan to abandon their rally sites at the Lat Phrao five way intersection and Victory Monument and move to Lumpini Park.
People's Democratic Reform Committee (PDRC) secretary general Suthep Thaugsuban will lead protesters from Lat Phrao to Victory Monument, passing Ratchaprasong and ending up at Lumpini Park.
The protesters will move from Lat Phrao and Victory Monument to join the rally site at Lumpini Park for their safety after they were attacked by an unknown group of assailants.
Mr Suthep will also discuss with Phra Buddha Issara who led demonstrations at the Government Complex at Chaengwattana to move that group of protesters to Lumpini Park.