Two men are trapped in a room with no doors or windows. They are standing on a floor of solid concrete. There is only one object in the room: a gun with only one bullet left. How do they escape?

I have no idea what the answer is, so I’m relying on you internet brainboxes. Also if you think a particular comment is the correct one, upvote it so everyone sees it.<br><br>Edit: Holy crap this got popular. If you want more of these mystery things I’d recommend checking out r/confession. Really interesting stuff. <br>Edit 2: Well, I didn’t expect this to blow up while I was at work. I’ll give everyone their gold in the morning. Thank you all so much. Also, if I had a dollar for every time I get told I ripped something off, I’d have around four dollars by now.