Terrie Durham and Todd Brundidge, both executive assistants in Building 197, said they were shuffling people out of the exit on their floor when the shooter walked into the hall and started firing.

“I could see his face,” Ms Durham said. “He looked around and fired. We were lucky he was a bad shot.”

Mr. Brundidge said the hallway between the shooter and himself was about 30 yards.

He could see the shooter was a man dressed in what appeared to be blue clothing. He said he could not tell if it was a uniform.

Asked whether the gunman said anything, Ms. Durham said “not a word. He raised the gun and started firing....