Cheese!

Gizmodo profiles an archival photo of a camera attached to a .38 revolver:

From General interwebs

The caption along with the picture only says it was used in 1938 New York. The picture looks legitimate as the gun, and camera technology match the time period. The few pictures taken by the gun make us think it was actually used by somebody at least once in its lifetime.

Looking at the pictures taken by the gun, the camera was cleverly tied to the trigger mechanism, so you could shoot a picture of your target before you shot them with your gun.

I suspect it was an attempt at documenting police shootings. It's an application far beyond the technology of the time, but I don't see why it couldn't be done today.