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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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." 

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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. 

The cause of the blaze was not immediately clear. 

"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!"