The robber wore all black clothing and a mask and carried a handgun, Riverhead Town police said.
He also was able to elude a K-9 search dog — and arrest — after he robbed the Citgo gas station on Osborne Avenue in Riverhead on Wednesday, police said.
Police said the suspect entered the station at 9:47 p.m., flashed the gun, demanded cash — and fled the scene on foot.
Now detectives are asking anyone with information about the suspect or the crime to call them at 631-727-4500.
All calls will remain confidential.