A 5-year-old boy with a history of starting fires ignited the blaze Sunday that claimed the life of his cousin, Pennsylvania authorities said, according to The Pittsburgh Post-Gazette.
The boy was not identified in the report, but he reportedly used a lighter to start the fire. Children under the age of 10 reportedly cannot be prosecuted for homicide in Pennsylvania.
"This is arson," Stephen A. Zappala Jr., the Allegheny County district attorney, said.
Three others were able to escape the house, but the 2-year-old cousin died of smoke inhalation in an upstairs room, the report said.
The boy who allegedly started the fire is being evaluated by the state's Children, Youth and Families division and may be removed from his family, the report said.