The description given of the man who shot Waco was that he appeared to be around Mike Stone's age. Karl Malden was 11 years older than Murray Hamilton, who played his revenge-seeking former partner Barney Lujack.
About 6 minutes into the episode, you can see a crowd of people watching the filming (and a police officer directing traffic) as Karl Malden and Michael Douglas walk across the street.
In the final scene, Stone is next to a water fountain sculpture that has an pattern supporting the base that looks eerily like the face in the painting, 'The Scream'.