The Boston Fire Department is hailing a "heroic job" by a next-door neighbor who officials say helped save a mother and two children from a raging 3-alarm blaze. 

The fire broke out around 12:10 a.m. Saturday in a two-and-a-half story building in the city’s Roslindale neighborhood. 

"A heroic job by the next door neighbor to save a mother and her 2 children who were trapped on the 2nd floor by heavy fire at the 3-alarm fire on Delford St," the Boston Fire Department said in a tweet. "He put a mattress down for them to jump as he caught the 5-year-old that the mother dropped out the window to him." 

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Boston Roslindale Massachusetts house fire

Boston Fire Department responds to the 3-alarm blaze early Saturday at a property in the city's Roslindale neighborhood. (Boston Fire Department)

The inferno is estimated to have caused $1 million in damage to the property. 

The Boston Fire Department said that "radiant heat from the volume of fire melted the siding on the adjacent building." 

Massachusetts home damaged by fire

The heat being thrown from the fire melted away the siding of an adjacent building, the Boston Fire Department says. (Boston Fire Department)

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Ultimately, five adults and four children were displaced as a result of the fire. Two firefighters suffered minor injuries while putting out the flames. 

Boston firefighters put out fire

The aftermath of the fire in Roslindale, in Boston, Mass., early Saturday. ( Boston Fire Department)

The cause of the blaze was not immediately clear. 

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"Quick decisions by the Command staff, and a coordinated effort by our Fire Alarm Division, allowed our Firefighters to aggressively attack the fire internally & externally, and keep it contained to 1 building," the Boston Fire Department said. "Great job by all!"