The first Death Star was destroyed in the Battle of Yavin and everyone aboard was lost. Though the Rebel Alliance official reports put the death toll at around a million Imperials, that estimate is based on intelligence about the minimum crew requirements to operate the Death Star. The Imperials tell a different story.
Imperial analysts claim that between 800 million to a billion people were lost in the “Yavin Massacre” This number is based on the flood of missing personnel reports filed in a period of 18 months after the Battle of Yavin. Imperial loyalists claim that the Alliance is intentionally down-playing the loss of life to distract from the fact that the destruction of the Death Star was an equally catastrophic loss of life as the destruction of Alderaan. The crew manifest of the Death Star was classified and destroyed with the station, so the truth may never be known.