According to my mother, her sister had epilepsy. It was plausible that while Jessie was driving Francie had a seizure, perhaps causing a momentary distraction. Jesse lost control of the wheel, and the car crashed into a concrete barrier. He was killed instantly. Francie died the following day, Friday March 14, 1969.
They are both buried in the Phillips family plot, section 7, at Earthman Resthaven Cemetery in Houston, Texas.