Judging from the scenery this was filmed in the Oxford, MS, housing projects which are located directly across from the one and only police sub station. That may explain Harry Sr.'s nervousness but I don't know what's up with the nails.

Fucked up but I understand it.
My grandfather was in a WWI tank. Although he saw his crew burnt needlessly to death in front of him for absolutely no reason, he still defended the war solely out of loyalty to his men and family. It's how they get people to continue supporting war.