Officer Kost was walking a foot beat near Boren Avenue and Terrace Street with a civilian friend, Lyle Smith, just before midnight on December 10. Kost had been with the Seattle Police Department for only a few months. The officer spotted three men he had reason to believe had just robbed a pharmacy for narcotics. Kost attempted to arrest all three by himself. In the struggle, Kost was shot in the back. Kost's companion used a call box to summon help.
Kost died two days later. Before he died, Kost identified a photograph of armed robber George W. Gunther as that of his assailant.
Two men were later arrested in San Francisco in connection with the death of a police officer there. These men admitted to killing Kost.