Luci Baines Johnson was in high school in Washington when the assassination occurred 50 years ago and had no idea if her mother and father had been killed as well.
"No one ever said a word about my father or mother. No one said a word period," said Johnson, who spoke publicly for the first time about that day in an interview on CBS' "Face the Nation."
Johnson said that when classes at National Cathedral School were canceled for the day, she was in a daze and panicked when she saw a grim Secret Service agent on campus.
"I looked over and saw that the Secret Service had very thoughtfully sent a man I knew, one of my father's detail -- and I turned and ran in the other direction as if I could run away from the inevitable," she said. "Of course, I wasn't capable of outrunning a Secret Service agent."
The agent told the 16-year-old Johnson her parents were alive and well, but Luci said her life was never the same. "Obviously, the people that it affected most of all were Mrs. Kennedy and her family," she said. "The rest of us were simply a backdrop, feeling their pain and wanting to comfort them, and knowing that they couldn't."
"For me, it was a moment that changed my world for always," Johnson added. "It was a day that will ring with pain and respect for as long as I live."