FBI Special Agent in Charge Matthew DeSarno said late Monday morning that Brian Isaack Clyde was pronounced dead at a hospital after the shooting outside the downtown Earle Cabell Federal Building.
DeSarno said they have no information indicating there were other shooters or other threats to the community.
A bomb squad meanwhile has been conducting controlled explosions of a vehicle associated with Clyde.
The Dallas Morning News reports that one of its photographers outside the building witnessed a gunman opening fire. A photograph shows authorities tending to a man lying on the ground in a parking lot outside the building.
The shooting left the windows of a revolving door shattered at the courthouse.