The car wreck.

On November 13, 1974, 28-year-old Karen Silkwood was killed in
a car accident near Crescent, Oklahoma, north of Oklahoma City. Silkwood worked as a technician at a plutonium plant operated
by the Kerr-McGee Corporation, and she had been critical of the
plant’s health and safety procedures. In September, she had
complained to the Atomic Energy Commission about unsafe
conditions at the plant (a week before her death, plant monitors
had found that she was contaminated with radioactivity herself),
and the night she died, she was on her way to a meeting with a
union representative and a reporter for The New York Times,
reportedly with a folder full of documents that proved that Kerr-
McGee was acting negligently when it came to worker safety at
the plant. However, no such folder was found in the wreckage
of her car, lending credence to the theory that someone had
forced her off the road to prevent her from telling what she
knew.