MIAMI SPRINGS, Fla.: The FBI is investigating whether suspected serial killer Andrew Cunanan is responsible for the murder of a homosexual physician 15 miles from the mansion where Italian fashion designer Gianni Versace was shot Tuesday. Dade County police cautioned, however, that the FBI has so far found only slight similarities between a man seen running from the murder scene (and captured on an indistinct video) and Cunanan. A witness described the fleeing man as white, in his late 20s, dark-haired and approximately 5 feet 10 inches tall. Meanwhile, police have issued an all-points bulletin for a stolen black Nissan Pathfinder (Florida license plate LLM-782), thought to have been driven by Cunanan, and are scrutinizing a hotel security camera videotape which shows a man similar to the fugitive running down a nearby alleyway shortly after Versace's killing. In an effort to scrape up further leads, Attorney General Janet Reno and New offered a $10,000 reward for information leading to Cunanan's capture. New York City Mayor Giuliani is offering an identical reward.