Laura Bush still has a hard time explaining how it happened, but when she was 17 on a November night in1963 she ran a stop sign in her hometown, struck another car and killed the driver, a 17-year-old boy who was a good friend of hers.
But there is no uncertainty about her feelings or the psychic toll 45 years of guilt has taken on the former first lady.
"In the aftermath all I felt was guilty, very guilty," Bush writes in "Spoken from the Heart," a new memoir that comes out next month and which was obtained by ABC News.
"In fact I still do. It is a guilt I will carry for the rest of my life, far more visible to me that the scar etched in the bump of my knee."
Writing publicly for the first time about the accident, Bush says the boy she killed, Mike Douglas, was not her boyfriend "though some in the press have claimed that he was." But he was a "very close friend" with whom she regularly talked on the phone.
The account of the crash is a deeply personal reflection on her feelings and faith. She writes how as an adult she has attempted to seek solace by offering advice to other young people responsible for fatal accidents.
And she writes about the boy who died.
"All through high school, Mike and I were good friends. We talked on the phone for hours, and Mike's circle of friends included nearly all of my own. And so it was unbelievable that it was his car in that almost always empty intersection," she writes.
Bush was driving with a friend on the evening of a school holiday and she blames a combination elements, including her own shortcomings, for the crash.
"A dangerous intersection, a less than safe car [Douglas drove a Corvair, made famous by Ralph Nader's 'Unsafe at Any Speed'] and me. I don't see well, I didn't ever see well, and maybe that played a part. Or perhaps it was simply dark. Judy and I were talking and I was an inexperienced driver who got to a corner before I expected it," Bush writes.
She remembers that in the aftermath of the accident she prayed that no one would be seriously hurt, but her prayer went unanswered.
Bush says she did not attend Douglas' funeral and avoided his parents, a decision she has regretted her entire life.
"I didn't go to the funeral. It was held that Saturday, November 9, at St. Mark's Methodist Church. I wanted to go and told Mother and Daddy that I wanted to go. But they wanted me to stay home. No doubt they were trying to protect me, thinking that it would be too hard on me and the Douglases if were to attend," she wrote.
"Looking back it now, with the wisdom of another 45 years, I know that I should have gone to see the Douglases; I should have reached out to them. At 17 I assumed that they would prefer I vanish, that I would only remind them of their loss."
The accident and the regret from not visiting the boy's parents reverberated in her life, and she writes of a particular empathy for parents who lose children, particularly after she became the mother of twins, Barbara and Jenna.