CENTRAL ISLIP - Police have arrested a suspect known as the "Superman robber" in connection with a three-year crime spree which they say earned him more than $250,000. The Suffolk County District Attorney's Office says 51-year-old William Dougherty, of Yaphank, who has become known for his cap emblazoned with the Superman symbol, was caught on surveillance camera before he held up a Stony Brook Sports Authority in August. Prosecutors say Dougherty's crime spree began to unravel last month when he walked into a Lake Grove Fortunoff and pulled out what appeared to be a gun. They say he demanded that store employees lock the doors and empty the registers, but one store worker escaped. Following a struggle with two of the Fortunoff employees in the parking lot, officials say Dougherty fled the scene, but he left behind traces of his blood on the ground. Police were eventually able to get a DNA match, leading to Dougherty's arrest.According to prosecutors, Dougherty held up three other retail outlets. In the 1990s, Dougherty pleaded guilty to burglarizing two personal storage facilities. Today, Dougherty pleaded not guilty to four counts of first-degree robbery and one count of attempted robbery. He remains behind bars on $5 million cash bail. Dougherty is due back in court Dec. 5.