"The next day, he woke up and he had a urinal tract infection which turned into septic shock," Neil said.
He was at an event honoring his late mother, former first lady Barbara Bush.
Neil also said his father would be going to Maine.
"I know many of his friends are excited that he is going to go to Maine and live a full, happy and comfortable life as long as he can," Neil said.
Neil and members of the Barbara Bush Houston Literacy Foundation wrote messages on the frame of a new home in Braes Heights.
The messages were in tribute to the former first lady's motto.
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