Such a film could never be made today...
...because today, we would get a twenty-minute exposition piece on the Young Man, his past, his motivations and the places he hangs out in - plus there would be a a "shocking revelation" in the end that - wow! - decades earlier Young Man was actually Harry's neighbors' kid, Young Boy, and Harry's dog broke Young Boy's toy rollercoaster, causing him to harbor homicidal tendencies from then on.