Baker was injured while serving as a firefighter in Kuwait in the 1990s when a Scud missile struck his barracks. Diane Zellner said he had seemed healthy enough to undertake the bike trip.
"He was doing well, so this kind of took us by surprise," she said.
Baker struggled with his health, but what people admired about him was how he moved forward despite his health problems and disabilities, she said.
"He struggled every day, but he lived, he was going to do what he wanted to do," she said.
Before he died, Baker made several blog posts from the road that can be read at www.honorandremember.org/kevin.html. His last post was Wednesday near Sherman, Texas.
He said the weather was raining and 34 degrees, so he said the Honor Guard from Louisiana would pick him up and take him somewhere warmer.
"He was doing something he loved," Diane Zellner said. "This was something he was passionate about."