This film is NOT a period piece -- nor is it supposed to be one! Anyone who proceeds from this assumption was obviously not paying attention to the film. First off, the sniper in the film is not named Charles Whitman, but WALT Whitman.
Anyone panning this imaginative film based on it being "poorly researched" (as does the comment immediately before this one) tells us more about his ability to comprehend information than he does about the movie itself.
Instead, DELICATE ART OF THE RIFLE tells us much about the nature of reality. Launching from Shakespeare's line about all the world being a stage, the film then goes on to expand upon this metaphor by suggesting that most of the things that affect the world lurk behind the scenes; and as in the theatre, most of what happens on stage is affected by things that are invisible.