A Petaluma bank robber has been arrested three months after the crime. On December 8th of last year, the Exchange Bank on North McDowell Boulevard was robbed for an undisclosed amount of money. After an investigation, police determined that 27-year-old Mason Brown of Cotati was responsible for the bank robbery. Yesterday, an officer pulled Brown over and arrested him. A search was then conducted on his home in Cotati where police recovered more evidence linked to the crime.