Last night I’m watching Columbo Goes to College and I’m confused how in the end their Toyota truck could have fired a gun, I mean the gun was removed and planted in the green car.
It’s illogical for him to assume there was still a gun mounted in the truck when he already located the gun, and even more unreasonable for any gun to be there and fire. I mean, what the kids removed the 45 planted it in the green car and then installed another gun in its place?
Am I missing something?

Yes that's right, the police deployed the gun back under the hood.

Another question is how Columbo dares to fiddle with the dummie and the same time asks the murderer to unlock the car when he knows that the gun will fire.