A Bridgeport man who robbed the Subway on Ethan Allen Highway at knifepoint back in May has been\u00a0arrested on a federal robbery charge.\u00a0 Ridgefield police said Alvin Robertson, 55, was indicted on Oct. 16 and faces four additional federal robbery charges for allegedly committing armed robbery at three Connecticut banks and another Subway restaurant in Monroe. \u201cThrough a collaborated effort with the FBI, Watertown PD, and Monroe PD, Alvin Robertson was apprehended,\u201d a Ridgefield police report said. According to the report, Robertson walked into the Ridgefield Subway across from the Branchville train station on May 20, where he brandished a knife and demanded all the money in the cash register. He fled with the money, which police later told The Press was $342 in cash. Robertson\u2019s face was allegedly caught on a surveillance camera in the store. Police later circulated a photo of the suspect displaying a knife in front of the store counter. The Connecticut Post reported on Sept. 28 that Robertson was charged for taking part in 11 bank robberies over five years in the 1990\u2019s, for which he was sentenced to 15 years in prison. Monroe Police traced two robberies to Robertson \u2014 the robbery of the Monroe Subway and a People\u2019s bank, both on Route 111 \u2014 after his \u201cvehicle became a point that was consistent in various robberies,\u201d Monroe Police Capt. Keith White was quoted in the CT Post.