Human remains have been found at the scene of a blaze in New York State where two volunteer firefighters were shot dead on Monday morning.
They were ambushed by William Spengler, 62, at about 6am when they arrived to fight the fire.
Police believe the remains to be those of Spengler's sister, Cheryl 67.
Spengler was found dead of a self-inflicted gunshot wound on Monday.
He and his sister lived with their mother until her death in October.
Spengler spent 17 years in prison after being convicted in 1981 of killing his grandmother with a hammer. He was granted parole in 1998.
As a convicted criminal, he was not allowed to own weapons.
Webster Police Chief Gerald Pickering said Spengler left a note indicating his intentions.
The three-page typewritten message talked about his intention to ''see how much of the neighborhood I can burn down and do what I like doing best - killing people''.
Two other firefighters who were wounded in the ambush. They are now in a stable condition after surgery. An off-duty police officer was also shot and wounded.
Chief Pickering said Spengler had three guns and aimed to burn down the neighbourhood.
He used a .38 calibre revolver, a 12-gauge shotgun and a Bushmaster .223 calibre rifle with flash suppression.
The same make and calibre rifle were used in the murders of 20 children and six adults at Sandy Hook School in Newtown, Connecticut, on 14 December.
Seven houses were destroyed by the fire.