The DeKalb County school bookkeeper thrust into the spotlight last August when she talked down an armed campus intruder stepped back into the limelight Tuesday to promote a book she has written about the incident.

Antoinette Tuff was at work in the front office of the McNair Discovery Learning Academy on Aug. 20, 2013, when an armed man entered the school with a rifle and several hundred rounds of ammunition.

Tuff talked that man, identified by police as 20-year-old Michael Brandon Hill, into surrendering to officers. No one was injured, although police said Hill fired shots at responding officers.

Tuff appeared on Good Morning America Tuesday to discuss her new book, “Prepared for a Purpose: The Inspiring Story of How One Woman Saved an Atlanta School Under Seige.”

In a one-on-one interview with GMA’s Robin Roberts, Tuff said that while it was difficult to relive the day while writing the book, “I know that the story needed to be told. I wanted people to get the foundation of what was actually going on.”

Tuff said she considers herself not a hero, but “one of God’s vessels - just going out to make sure I do His work and do His will.”

She said that the day her school came under seige, “I just sat there and said, ‘okay, God, tell me what to do and how to do it.’ “

“Remember, I was terrified on the inside,” Tuff told Roberts. “You’ve got this gentleman, he’s already telling you that everybody’s going to die and you see it in his eyes, see it in his movement.”

She said she was just trying to “say the right words so that everybody at the end can get out alive, including him.”