WEBSTER, N.Y. — It was a simple call to put out a car fire, the sort of routine job that firefighters tackle all the time. The fire truck hurtled to the assignment early Monday in this drowsy town on the shores of Lake Ontario that was preparing for the joys of Christmas.

But it apparently was a trap, the authorities said. There were a house and a car burning. There was also a waiting killer, who had stationed himself like a sniper on a berm above the firefighters.

Before they could begin to extinguish the fire, the firefighters were met by a burst of gunfire. Four were hit by the volley of bullets, and two died. An off-duty police officer from nearby Greece, N.Y., who was on his way to work, was wounded when he and his car were hit by shrapnel.

For a few hours, the scene was chaotic: Flames ignited adjacent houses as the police frantically searched for the gunman.

They would find him dead near the beach, with a self-inflicted gunshot to the head. He was identified as William Spengler, 62, a man with a lengthy criminal record, who lived in the burning house. In 1981, he pleaded guilty to manslaughter for bludgeoning his 92-year-old grandmother to death with a hammer. He was imprisoned until 1998.

He remained on supervised parole until 2006, and the Webster police said they had not had recent brushes with him. His mother, Arline, who lived in the same house, died this year. A former neighbor, Roger Vercruysse, said Spengler and his sister had also lived in the house, but “he stayed in one part with his mother and his sister stayed in the other part, and they never talked to each other.”

Spengler’s ire for his sister was matched by love for his mother, Vercruysse said.

Spengler did not seem to have a lot of friends, but “every time I needed help, he was there,” Vercruysse, 64, said

The police said they found Spengler with three weapons by his side, including the rifle used in the shootings. Authorities said that they did not know where he got the weapons, but that there had been recent gun thefts in Monroe County, where Webster is. As a felon, Spengler was prohibited from owning guns.

Authorities said they were unaware of a motive, but Gerald Pickering, the police chief in Webster, suggested that “there were certainly mental health issues involved.”