The book Death at Every Stop , by Wesley Clarkson, concludes with an excellent summary, citing the views of psychiatrists and criminologists, of what might have triggered Cunanan. Following are some of their remarks that not only examine a possible motive but help illuminate the psyche that was Andrew Cunanan. A lot of folks who do this feel a sense of superiority over the police. The police were basically impotent to him. By doing this, he not only got to validate his own superiority, he got to make a statement.
Most serial killers are much more discrete, careful to hide the bodies.
He was kind of like the Unabomber, who kept sending out more letters. Most serial killers would never use a firearm. There is no comparison between Cunanan and any other model we have. He was having financial problems. All of these dynamics were pulling on this guy.