A gunman ambushed four volunteer firefighters responding to an intense pre-dawn house fire on Monday morning in a town in western New York State, shooting four and killing two before ending up dead himself, authorities said.

The gunman fired at the firefighters when they arrived shortly after 5.30am at the blaze near the Lake Ontario shore in the town of Webster, police chief Gerald Pickering said. The first police officer who arrived exchanged gunfire with the suspect, authorities said.

One of the two dead firefighters is also a town police lieutenant; it was not clear whether he returned fire. An off-duty police officer who was driving by has injuries from shrapnel, Mr Pickering said.

Two wounded firefighters were in critical condition, authorities said.

The fire started in one home and spread to two others and a car, officials said. The gunfire initially kept firefighters from battling the blazes. Police say four homes were destroyed and four damaged.

The West Webster Fire District learned of the fire early on Monday after a report of a car and house on fire on a narrow peninsula where Irondequoit Bay meets Lake Ontario, Sheriff Patrick O'Flynn said.

The fire appeared from a distance as a pulsating ball of flame glowing against the early morning sky, flames licking into treetops and reflecting on the water, with huge bursts of smoke billowing away in a brisk wind.

Monday's shooting and fires occurred in a neighbourhood of seasonal and year-round homes set close together across the road from the lakeshore. The area is popular with recreational boaters but is normally quiet this time of year, Mr O'Flynn said.

Mr O'Flynn lamented the violence, which comes on the heels of other shootings including the massacre of 20 students and six adults at Sandy Hook Elementary School in Newtown, Connecticut.

"It's sad to see that that this is becoming more commonplace in communities across the nation," Mr O'Flynn said.

Webster, a middle-class, lakeside suburb, is now the scene of violence linked to house fires for two Decembers in a row.

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