Blade Runner / FAQ / Gaff and Deckard's gun
How Did Gaff Get Deckard's Gun?
Deckard sits on the roof for a long time. In the Workprint, Deckard says
he watched him die all night and that it was a slow, painful thing. Gaff
may have followed Deckard's groundcar, or checked out the radio reports of
Sebastian's death, walked around to piece things together and found
Deckard's gun. It would also be in character if Gaff was simply lurking
in the background hoping for Deckard to get himself killed.