Police used to use revolvers as their duty sidearm not that long ago. By the mid 1990's most police departments had switched over to semiautomatic pistols for their service weapons, often trading in their inventories of revolvers, which were typically subsequently liquidated onto the civilian market.
It should be noted that some police departments across the United States began to transition from revolvers to semiautomatic pistols beginning as early as the late 1960's, but most departments maintained the revolver as their issued sidearm for several more decades.
