gun control and my three year old

So what would you say to this boy:

if he handed you this toy:

( A geotrax bridge support for his train set)

and asked you to turn it into this:
I asked him why he wanted me to do it, and he said in his most big boy three year old voice

"to get those bad guys!" he then said "go like this" and held his arm up as if holding a gun and waved it at the living room ceiling.

My son doesn't know the word gun, it's not really a word that comes up much in our little world, and the one or two times it has we spell it, because I don't think it's a word he needs to know. He doesn't own any toy guns, not even squirt guns.

My son doesn't know what a gun does. He doesn't really even understand the concept of hurting another person beyond playgroup roughness, or how he needs to be gentle with his baby brother. I know he doesn't understand the concept of death. He only watches children's tv (pbs, disney), we don't even watch the news with him around, and he hates movies, and has absolutely not seen one that would tell him how a gun is used.

I have no idea where he got the idea to make a gun out of train track support, maybe the ymca, maybe his older cousins. I know he doesn't understand it.

I pulled off one leg for him and handed it back, why? Because I felt his limited idea of what he wanted to do with it was far less damaging than me making a big deal out of something he doesn't understand and calling his attention to it.

As soon as I handed it to him a little girl was at our front door to play for the morning. He no sooner had it in his hand then he tossed it on the couch and ran to go play with his friend.

So what would you have done?