New York City officials now believe the devastating Thursday night Bronx fire that killed 12 people—including four children—was caused by a 3 1/2-year-old boy playing with a stove in an apartment. Mayor Bill de Blasio told reporters that four people remained in critical condition late Friday morning. Among the dead were girls ages 1, 2, and 7, and a boy whose age has not been released. The flames moved so quickly, in part because of a gas line that fueled the fire, that most residents of the apartment complex never made it out of their homes on the frigid night. Those who escaped the five-story building stood barefoot in the cold without coats, watching their neighbors' burned bodies carried away on stretchers. Fire Commissioner Daniel Nigro called the blaze “historic in its magnitude.” “It is an unspeakable tragedy, and families have been torn apart,” de Blasio said.