the captive bolt pistol or stunner used

episode #1." horse sense".

vet examines a horse, decides it needs to be put down, the owner of the horse argues with him. during the argument the vet says " he has a humane killer", "put him down", and "shoot him".

the vet then goes to his car, takes out what looks like an 8" X 1" piece of pipe and removes something from the dashboard. pulls it out of the dash, like a radio knob, looks at it, as if it to check something, goes into the barn( you dont see what he does) next you hear what sounds like a very low power gun shot, more like a "ramset" power tool that sets bolts with gun powder.

anybody know what he used?

i asked this elsewhere and many guessed a captive bolt pistol or stunner. it drove a bolt into the horses head, either by spring, compressed air or gunpowder.
but no one can explain what he removed from the dash board.
cigarette lighter, to light the gun powder, was guessed, but that does not sound right. the cigarette lighter would have cooled off by the time he reached the barn, and if the gun powder was left in the pistol, in the car, it would have been destroyed by moisture.

if you know what it was, do you know of a link to a museum, or someplace that will describe how it worked?