Walmart sells air pistols that are much quieter than shotguns. My neighbor has one and we have many fewer squirrels as a result. I keep asking Santa for a red rider bb gun. PA actually has a "squirrel hunting season" so it would be perfectly legal to shoot them then, if you had a hunting license.
I hate the tree rats. The like to plant black walnuts in my garden. They are too lazy to dig the uncultivated soil, arghhh.