"Come on up here," Gareth called down. "Long as you don't give us any reason to x we won't hurt you. If we can all be civil I think we might be able to find a few things to talk about.

As he spoke he backed up, away from the window and took a seat at the table where he'd piled all the food and supplies from his bag. 

Reaching under the table he pulled a large handgun from where it was held to the under side with a strip of velcro and pulled it from the holster before setting it down on the table in front of him.  The gun would be in full view when their visitor came in through the window. 

The guy didn't have to know that there weren't any bullets. Or that Gareth had already cannibalized the slide spring and firing pin for other uses.