The assault rifle was believed to be the weapon that struck down the firefighters. He then killed himself as seven houses burned on a sliver of land along Lake Ontario. His body was not found on a nearby beach until hours afterward.
Residents of the suburban Rochester neighborhood who left their homes during the fire were allowed to return Tuesday. Police SWAT team members had used an armored vehicle to evacuate more than 30 residents.
Spengler's motive was left unclear, Pickering said, even as authorities began analyzing a two- to three-page typewritten rambling note Spengler left behind.
He declined to reveal the note's full content or say where it was found. He read only one chilling line: "I still have to get ready to see how much of the neighborhood I can burn down, and do what I like doing best, killing people."
Pickering added: "There was some rambling in there and some intelligence we need to follow up on."
It remained unknown what set Spengler off but a next-door neighbor, Roger Vercruysse, noted that he loved his mother, Arline, who died in October after living in the house in a neighborhood of seasonal and year-round homes across the road from a lakeshore popular with recreational boaters.
Pickering said it was unclear whether the person believed to be Spengler's sister died before or during the fire.
"It was a raging inferno in there," Pickering said.
As Pickering described it and as emergency radio communications on the scene showed, the heavily armed Spengler took a position behind a small hill by the house as four firefighters arrived after 5:30 a.m. to extinguish the fire: two on a fire truck; two in their own vehicles.
Several firefighters went beneath the truck to shield themselves as an off-duty police officer who came to the scene pulled his vehicle alongside the truck to try to shield them, authorities said.