At around midnight, fire crews arrived at home in flames, in the 12000 block of Point Longstreet Way, according to the Prince William County Fire and Rescue System.
Two adults and a child were inside the home and started to evacuate away from the flames, authorities said.
One of the adults, who successfully got the family's dog out of the burning house, sustained life-threatening injuries during the incident, officials reported.
Fire crews said they found the man laying outside the home and he was transported to a local burn center.
The Fire Marshal's Office believed the fire was accidental, but the home was deemed unsafe to live in, officials said.
After the incident, the family was assisted by the American Red Cross, authorities said.
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