A Bridgeport man who robbed the Subway on Ethan Allen Highway at knifepoint in May 2018 pleaded guilty to one count of bank robbery before U.S. District Judge Victor A. Bolden on Tuesday.Alvin Robertson, 56, also\u00a0admitted that he committed a total of three bank robberies and two Subway store robberies in Connecticut last year, according to U.S. Attorney John H. Durham.\u00a0According to court documents and statements made in court, on May 20, 2018, Robertson robbed a Subway store located at 9 Ethan Allen Highway in Ridgefield. During the robbery Robertson brandished a knife, pointed it at the store clerk and stated, "Give me all your money or I will kill you."On July 22, 2018, Robertson robbed a Subway store located at 447 Monroe Turnpike in Monroe. During the robbery, Robertson indicated that he had a gun.Robertson also robbed a People's United Bank branch at 470 Monroe Turnpike in Monroe on August 29, 2018; a People's United Bank branch at 763 Straits Turnpike in Watertown on September 21, 2018, and a People's United Bank branch at 1135 Farmington Avenue in Berlin on September 25, 2018.Robertson has been detained since his arrest on related state charges on September 27, 2018. At sentencing, he faces a maximum term of imprisonment of 20 years. A sentencing date is not scheduled.Robertson has prior federal and state bank robbery convictions.This matter is being investigated by the Federal Bureau of Investigation and the Watertown, Ridgefield, Monroe and Berlin Police Departments. The case is being prosecuted by Assistant U.S. Attorney Douglas P. Morabito.