WEBSTER, N.Y.—A gunman ambushed four volunteer firefighters responding to an intense pre-dawn house fire Monday morning outside Rochester, killing two, wounding two others and then killing himself, authorities said. Police used an armoured vehicle to evacuate more than 30 nearby residents.

The gunman fired at the firefighters when they arrived shortly after 5:30 a.m. at the blaze near the Lake Ontario shore in Webster, town Police Chief Gerald Pickering said. The first Webster police officer who arrived chased the suspect and exchanged gunfire with him, authorities said.

“It does appear it was a trap” for the first responders to the fire, Pickering said at a news conference.

The gunman, William Spengler, had served more than 17 years in prison for beating his 92-year-old grandmother to death in 1980 at the house next to where Monday’s attack happened, Pickering said. Spengler, 62, was paroled in 1998 and had led a quiet life since, authorities said. Convicted felons are not allowed to possess weapons.

Police say he set fire to a car and house to lure firefighters to his home on the shore of Lake Ontario. When they arrived, he opened fire from outdoors, probably with a rifle and from atop an earthen berm.

“He laid in wait with armament and shot first responders,” Pickering said. Police don’t know a motive yet.

Two firefighters, one of whom was also a town police lieutenant, died at the scene, and two others were hospitalized. A fifth man who was passing by was also injured. The police officer who exchanged gunfire with Spengler and “in all likelihood saved many lives,” Pickering said.

Seven houses were destroyed in the blaze, Pickering said, and police have not been able to get inside the houses to determine if there are any more victims. They said Spengler’s 67-year-old sister Cheryl Spengler was unaccounted for. He lived in the house with his sister and mother, Arline, who died in October.

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 fire department learned of the blaze early Monday after a report of a car and house on fire on a narrow peninsula, Monroe County 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.

Two of the firefighters arrived on a fire engine and two in their own vehicles, Pickering said. After the gunman fired, one of the wounded men managed to flee, but the other three couldn’t because of flying gunfire.

A police armoured vehicle was used to recover two of the men, and eventually it evacuated 33 people from nearby homes, the police chief said.

The dead men were identified as Police Lt. Michael Chiapperini, 43, the Webster Police Department’s public information officer; and Tomasz Kaczowka, also an emergency dispatcher, whose age was not released.

Pickering described Chiapperini as a “lifetime firefighter” with nearly 20 years with the department, and called Kaczowka a “tremendous young man.”

The two wounded firefighters, Joseph Hofsetter and Theodore Scardino, were in guarded condition, authorities said. Both were awake and alert and are expected to recover.

Hofsetter was hit once in the pelvis, and the bullet lodged in his spine, authorities said. Scardino was hit in the chest and knee.

Monday’s shooting and fires were in a neighbourhood of seasonal and year-round homes. The area is popular with recreational boaters but is normally quiet this time of year.

“We have very few calls for service in that location,” Pickering said. “Webster is a tremendous community. We are a safe community, and to have a tragedy befall us like this is just horrendous.”

O’Flynn lamented the violence, which comes on the heels of other shootings including the massacre of 20 students and six adults at a school in Newtown, Conn.

“It’s sad to see that this is becoming more commonplace in communities across the nation,” O’Flynn said.