"Next time I talk to [God], I'm gonna ask him, 'Why me,'" Bob Ebeling said in January of his nagging guilt over the Challenger disaster, which he tried to prevent as an engineer with NASA contractor Morton Thiokol. He may now get his chance. The 89-year-old died Monday in Utah, after a battle with prostate cancer, reports NPR. Raised in Illinois, Ebeling moved to Utah and became a rocket scientist with Thiokol in 1962, per the Salt Lake Tribune. He was one of five engineers who tried to stop the Challenger launch, fearing the booster rockets' O-ring seals would fail in the cold. "He said, 'The Challenger's going to blow up. Everyone's going to die,'" daughter Leslie Ebeling Serna remembers of the morning of the launch. "He was beating his fist on the dashboard. He was frantic." Afterward, "he wept—loudly."
Ebeling retired soon after and helped restore Utah's Bear River Migratory Bird Refuge after a flood. He served as a volunteer there over the following decades, earning the Theodore Roosevelt Conservation Award in 1989 and the National Wildlife Refuge System Volunteer of the Year in 2012. Though he spoke about his persisting guilt over the Challenger disaster as recently as this year, Serna says it vanished before his death. Support for Ebeling had recently poured in, including from NASA, which said the disaster taught the agency "to remain vigilant and to listen to those like Mr. Ebeling who have the courage to speak up." "It was as if he got permission from the world," Serna says. "He was able to let that part of his life go." Ebeling put it best himself. "You helped bring my worrisome mind to ease," he said in thanking those who reached out to him. "You have to have an end to everything."