What could be considered symbolic in the short story, "Killings."

Keep in mind, symbols are objects in
the story that are meant to represent a deeper meaning.  Often, when looking for
symbolism, it is helpful to look for prominent objects, characters, or even places that
recur more than once in the story.  It also helps to look for seemingly insignificant
objects which the author seems to put undo attention on in a scene or
scenes.

In this case, the guns in "Killings" should be
looked at as symbolic.  Consider first that there are three guns of importance. 
Strout's gun, which killed Frank, Fowler's gun, which killed Strout, and Willis' gun,
which is not the impetus for any death in the story but is available to be one. 
Predominantly, guns seem to be the symbol for revenge.  Strout killed Frank as revenge
for sleeping with his wife.  Fowler killed Strout for the death of his son Frank.  If
you go back and read the story again, you will also notice how much description is given
to the guns.  Fowler, before killing Strout, frequently grips his gun in anticipation,
as if it is the object of relief for his pain, the object which provides him courage,
and finally, the object which finalizes his act of
revenge.

The suitcase Fowler forces Strout to pack (and
Strout's clean home) is symbolic of Strout's humanity and normalness outside of being a
killer.

Willis' wife's pain pills could be considered
symbolic of the fact that she and Ruth both go to sleep and ignore what their husbands
are out doing late at night, despite the fact that though it goes unspoken, they likely
know.