SALEM – A Saugus man who pretended to have a weapon in his pocket as he stole about $650 from a Route 1 gas station to buy clothing for his son may serve up to three years in state prison.Douglas G. Hurlbert, 51, of 43 School St., made his plea Tuesday afternoon in Salem Superior Court to a charge of armed robbery.He was sentenced to serve not less than a year and not more than three years in state prison by Judge John T. Lu.Assistant District Attorney Jennifer Kirshenbaum said the charges arise out of an incident in Saugus on the night of Oct. 10 when the suspect walked into the Super Petroleum Gas Station, located at 1330 Broadway, saying to the clerk he had a weapon while demanding all the $20 bills in the cash register.The frightened male clerk turned over about $650 in bills and Hurlbert fled from the establishment on foot down Felton Street.A store surveillance camera captured a clear picture of Hurlbert, wearing jeans and a brown Superman hat.As police were reviewing the video, a Saugus police officer recognized the robber as Hurlbert, saying he has known him for many years.Before applying for a warrant, police compared Hurlbert’s surveillance image with a photo on file at the Registry of Motor Vehicles.When police went to his home to arrest Hurlbert, he told police he didn’t remember the holdup because he was taking “Klonopins” and would have blackouts.He went on telling police that he was sorry and had given some of the cash stolen to his son who needed to buy clothes and some to his girlfriend.The punishment imposed is immediate, which eliminates any term of incarceration Hurlbert currently is serving on unrelated crimes.Hurlbert was indicted by an Essex County grand jury last November and has been held in custody in lieu of bail.A second charge of larceny over $250 was dropped as part of the plea concession reached by the prosecutor and defense.The judge agreed to credit Hurlbert the 40 days he has spent in jail awaiting trial on the case.