[Update: The employee had the day's deposit envelope in his hand when the robber arrived, according to a report on WHDH. The suspect demanded he drop the enbelope, then threatened the man's sister and demanded more money from the register.  12:20 a.m. Monday]

At around 9:30 p.m. Thursday night, a Harvard Street service station was reportedly robbed at gunpoint. 

A brother and sister were locking up at Shimon's Service Station, according to the Brookline Police Blog, when they were approached by a man with a handgun and a red handkercheif over his face. He entered the store and flashed the gun, then demanded money. 

Police reports indicate that the call was made from a back room, where the caller had been locked after the incident.

The suspect was described as a black man in his late teens or early 20s, about 5'7" or 5'8" tall with a thin build, wearing a white hoodie, blue jeans, and a red handkerchief covering his face. The incident log also notes he had a black backpack with white lettering along the straps. 

Brookline police were unable to locate the suspect afterward, and passed information about the incident to nearby agencies.