At 1:30 a.m., the suspect entered the gas station at 1129 E. Putnam Ave., brandishing a handgun and demanding cash, said Lt. Kraig Gray, public information officer.
The attendant, who was not injured, immediately complied with the demands, Gray said, and the suspect fled the store with a small amount of cash.
The suspect got into a waiting vehicle, described as possibly an older model gold-colored SUV, and fled the area, he said.
The suspect was described as a male with a light complexion, unknown age, and of average height with average build, Gray said.
The suspect was also wearing a plastic semi-opaque Halloween mask and sunglasses, a dark hoodie sweatshirt, brown jacket, dark colored pants and white sneakers, he said.
Anyone with any information about the armed robbery is asked to contact the Greenwich Police Tip Line at 203-622-3333 or 1-800-372-1176 or by email at tips@greenwichct.org.
Click here to follow Daily Voice Greenwich and receive free news updates.