A fire tore through a Broadway building in Somerville late Monday, destroying Rei Da Picanha restaurant and the barber shop beside it, and damaging nearby businesses with smoke and water. The fire began around 10 p.m. Oct. 12 while both businesses were closed and burned through the night, Somerville Fire Chief Charles Breen said. Firefighters initially entered the basement but withdrew when conditions became too dangerous, switching to an exterior attack. The blaze spread through the building before the roof collapsed. Breen described the fire as unusually difficult to fight, saying crews could not open walls and ceilings to reach flames once they moved to battling it from outside. Two firefighters suffered electrical shocks and were taken to a hospital for treatment. Both were released and are doing well, Breen said. No serious injuries were reported. The neighboring Santander Bank sustained smoke damage, and other nearby stores had smoke and water damage. The fire’s cause was not yet known. Fire crews were fortunate to contain the blaze before it consumed the entire business block, Breen said.