BROOKLYN - Six families in Bushwick were forced to evacuate Monday due to a four-alarm fire.Fire officials say the blaze started at 1285 Greene Avenue, a building that was vacant and boarded up. They say the fire spread to neighboring homes, forcing the evacuations.Sources tell News 12 Brooklyn that the fire was started by squatters living in the building. Neighbors say a man and a woman had been living there for about a month.The Red Cross took the six families to a local hotel to stay. Officials say four firefighters suffered minor injuries from the blaze.