A former Scarborough town councilor is facing up to 20 years in prison and a $250,000 fine after pleading guilty to bank robbery this week.

Robert Patch, 45, of Scarborough, will be sentenced on Aug. 14 after pleading guilty Thursday in federal District Court in Portland. He is being held in Cumberland County Jail.

Armed with a pellet gun, Patch entered a Maine Bank and Trust branch in Biddeford at about 10:45 a.m. on April 9, and demanded cash from a bank teller. He obtained about $4,000.

Bank employees took down Patch’s license plate number and a description of the truck he drove away in after the robbery. Patch was arrested in Saco about 15 minutes after the robbery. Police recovered both the pellet gun and the stolen cash from Patch’s truck.

After his arrest, Patch provided a written statement, confessing to the robbery, according to an affidavit. He told FBI Special Agent James Lechner that he “decided on the morning of April 9 to rob a bank.” Because bank deposits are federally insured, bank robbery is a federal crime.

Patch served on the Scarborough Town Council from November 2003 to November 2006. Scarborough Town Manager Ron Owens said Patch was an engaged member of the Town Council the first two years he was in office, but barely showed up to meetings the last year.