An "unknown white male" entered the gas station, in the 1000 block of Pulaski Highway, at about 1:30 a.m. that morning, according to a police press release.
Police did not receive a call until 8:32 a.m. The employee told police that while the employee was working, the robber came in, pulled a knife and demanded money from the register.
The victim complied, giving the robber an undisclosed amount of money, according to the release.
The robber ran in an unknown location. The investigation is ongoing.
This is the second robbery at the gas station in a year. Two men were recently arrested, one of whom is a Havre de Grace High School senior, in connection with an armed robbery there on Aug. 28, 2012.