Born in National City, California, Cunanan graduated from The Bishop's School in the La Jolla neighborhood of San Diego, California, in 1987.
Cunanan next drove to Chicago and killed prominent real-estate developer Lee Miglin, 72, on May 4, 1997. Five days later Cunanan, who escaped with Miglin's car, found his fourth victim in Pennsville, New Jersey, at the Finn's Point National Cemetery, killing caretaker William Reese, 45, on May 9, 1997. Cunanan apparently killed him for his pickup truck, while leaving Miglin's car behind. Following this murder, the first of a non-acquaintance, the FBI added him to its Ten Most Wanted list.
While the manhunt focused on Reese's truck, Cunanan hid in plain sight in Miami Beach, Florida, for two months between his fourth and fifth murders. He went out mostly to gay nightclubs, and made little attempt to disguise his appearance. He even used his own name to pawn a stolen item, knowing that police routinely check pawn shop records for stolen merchandise. Finally, Cunanan murdered fashion designer Gianni Versace, on July 15, 1997.
Eight days later, on July 23, 1997, Cunanan committed suicide by gunshot in the upstairs bedroom aboard a Miami houseboat apparently to avoid capture by the police, who finally discovered Reese's stolen truck nearby and obtained tips from neighbors that someone resembling Cunanan was living in the houseboat.
The gun used by Cunanan for some of the murders was a Taurus semi-automatic pistol in .40 S&W caliber, which had been left behind in California by first victim Jeff Trail when he relocated to the Midwest.
Police searched the houseboat where Cunanan died in order to piece together a motive for his cross-country killing spree. However, Cunanan left behind few personal belongings. This surprised investigators, given his reputation for acquiring money and expensive possessions from wealthy, older men. Police considered few of the findings to be of note, except multiple tubes of hydrocortisone cream and a fairly extensive collection of the fiction of C.S. Lewis.