chris pelon explains the inferno left little time for anybody to react. >> reporter: a dozen people are dead. and investigators say a young boy is to blame. >> we found this fire started in the kitchen on the first floor. it started from a young by, 3 1/2 years old playing with the burners on the stove. >> reporter: the fire broke out in a bronx apartment building thursday night. investigators say it spread quickly to other floors when the young boy's mother left her apartment door open as she escaped with her children. >> fire travels up, the stairway acted like a chimney. it took the fire so quickly upstairs that people had very little time to react. >> reporter: the flames forced dozens onto fire escapes and into the street. enduring brutal cold as firefighters tried to rescue them. >> we got people on the fire escape at the front of the building. >> reporter: joel rodriguez made it out alive. >> yanked the ac out the window, had my wife get out. >> reporter: 170 firefighters spent two hours battling the flames. the oldest victim, 56. the youngest, just eight months. >> there was a l