Police have found human remains in the burned-out home of the New York state ex-convict who killed two firefighters.
They believe the victim is the gunman's sister.
Police Chief Gerald Pickering said the remains were found in the charred house that 62-year-old William Spengler shared with his 67-year-old sister, Cheryl.
A medical examiner will need to determine the identity.
Police said William Spengler armed himself with a revolver, shotgun and military-style rifle before he set his house on fire to lure first responders into a pre-dawn death trap on Christmas Eve.
Mr Pickering says Spengler "was equipped to go to war".
Spengler killed himself as seven houses burned around him.
A friend said Spengler hated his sister, but police said a motive has yet to be determined.