The helicopter is cast into the body of the gun and has wires running into it. Looking at the wiring, there should be lights in the propeller but they're not be

The helicopter is cast into the body of the gun and has wires running into it. Looking at the wiring, there should be lights in the propeller but they're not being shown. So the propeller most likely just spins and makes trippy light patterns. It looks like there were some liberties taken with the editing to clean up the picture. There's a spring for the trigger return, which appears to double as a switch, but the trigger itself is missing. It looks like there should be a rotating cylinder on the barrel, as well.