UNIONDALE - Nassau police are searching for a man who held up a Uniondale gas station overnight. The incident occurred at the Sunoco station on Hempstead Turnpike at around 1 a.m. Police say the man flashed a knife and demanded workers open the cash register. Surveillance video captured images of the suspect taking money from the register. He got away with about $500, police say. Investigators say the man hopped into the passenger seat of a red, four-door sedan and took off. Anyone with information is urged to call Crime Stoppers at 1-800-244-TIPS.