The FBI’s Violent Crimes Task Force issued a statement Thursday describing the man and listing the five banks officials believe he has robbed since Dec. 10.
He is a 150-pound white male seen wearing a dark sweatshirt or jacket, black pants, black gloves, and dark brown or black boots/shoes with a black and/or gray brim beanie cap.
"While a weapon not been seen during the commission of any of the robberies, the suspect is considered armed and dangerous," the FBI said.
Braintree police said the man stole an unspecified amount of money from Braintree Cooperative Bank at about 2:30 p.m. on Monday, Dec. 23. He passed a note demanding money and claimed he had a weapon, but did not show one.
No one was hurt during the robbery.
Investigators said Thursday that the same man has allegedly robbed banks in Dorchester, Quincy, Stoughton and Needham over the last two weeks.
"The Brim Beanie Bandit enters the bank, approaches the teller, and either shows or leaves a note asking for money," the FBI said. "On all robberies, the bandit fled the bank in an unknown direction; it is unknown at this time if a vehicle is being used for transportation.
"The robberies and attempted robbery are being investigated by multiple law enforcement agencies including FBI Boston; Boston, Quincy, Stoughton, Needham, and Braintree Police Departments; and the Violent Crimes Task Force officer of the Massachusetts State Police.
"The FBI is offering a monetary reward for information leading directly to the arrest and charging of the robber. Anyone with information regarding the robbery should call the FBI’s Boston Division at (617) 742-5533 or the local police departments stated above in this release."