At whom does mr. nathan think he has fire the gun?

Mr. Nathan Radley thinks he has fired his gun to some thieves in his garden patch. When the children plan to spend Dill's last night in Maycomb, they plan to get in Mr. Radley's backyard. However, Mr. Radley is aware that there is something wrong going on so he fires his shotgun. He says he will kill anything that invades his property.  

The best answer in my opinion would be the last one. i hope this