JERICHO - ? Cops are searching for a masked gunman who held up a Nassau County gas station. Police say the man was wearing a skull mask and walked into a Gulf station on Jericho Turnpike around 11:30 p.m. Sunday. The man forced the employees to shut off the lights and hand him cash. The robber took off. Anyone with information is asked to call Nassau Crime Stoppers at 1-800-244-TIPS.