(CNN) -- The infamous "Onion Field" cop killer whose 1963 crime was chronicled in a best-selling book and a movie has died, officials said Monday. He was 79.
Gregory Powell died Sunday at the California Medical Facility, a prison in Vacaville, the California Department of Corrections and Rehabilitation said in a statement.
In October, Powell was denied compassionate release, all but guaranteeing he would die behind bars.
He had cancer, according to the Los Angeles Police Protective League. Prison officials, however, never confirmed that account and Monday's statement said simply that Powell died of "natural causes."
He was serving a life sentence with the possibility of parole for killing Los Angeles Police Officer Ian Campbell nearly 50 years ago.
The crime was chronicled in Joseph Wambaugh's best-selling book, "The Onion Field" and a movie by the same name.
On the night of March 9, 1963, Powell and accomplice Jimmy Lee Smith were driving around Los Angeles, looking for a liquor store to rob.
Campbell and his partner, Officer Karl Hettinger, pulled the two over in a routine stop. Powell, who was ordered out of the car, pointed a gun at Campbell's head. He and Smith disarmed both officers, took them hostage and drove to a remote onion field in Bakersfield, a town about 110 miles of north of downtown Los Angeles.
The officers were forced out of the car and ordered to stand with their hands above their heads. Powell said to them, "We told you we were going to let you guys go, but have you ever heard of the Little Lindbergh Law?"
"Yes," Campbell, 31, replied. Powell then shot him to death. Hettinger escaped, but the murder of his partner haunted him for the rest of his life.
Powell and Smith were sentenced to death in November 1963. Their sentences were commuted to life in prison with the possibility of parole in the early 1970s when the death penalty was declared unconstitutional.
Smith was paroled in 1982, but was in and out of prison in subsequent years for drug-related parole violations. He died at a California detention center in 2007.
The Little Lindbergh Law makes a kidnapping within the state a capital offense if the victim suffers death or other injury. Powell, however, erroneously believed the law made it a capital offense to kidnap a police officer.
The Little Lindbergh Law followed a federal law, nicknamed the Lindbergh Law, that made taking a kidnapped person across state lines a federal crime. That law was passed after the kidnapping and murder of the young son of aviator Charles Lindbergh in 1932.
CNN's Michael Martinez contributed to this report.