Pickering says Spengler "was equipped to go to war."
Spengler killed himself as seven houses burned around him. A friend said Spengler hated his sister but police say a motive hasn't been determined. The ex-con left a rambling typewritten note saying he wanted to burn down the neighborhood and "do what I like doing best, killing people," police said Tuesday.
One of the guns recovered was a military-style .223-caliber semiautomatic Bushmaster rifle with flash suppression, the same make and caliber weapon used in the elementary school massacre in Newtown, Conn., Pickering said.
The chief said police believe the firefighters were hit with shots from the rifle given the distance but the investigation was incomplete.
The two- to three-page typewritten note left by Spengler didn't give a motive for the shootings, Pickering said. He declined to divulge the note's full content or say where it was found, but read one line from it: "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."
About 100 people attended an impromptu memorial vigil Monday evening in Webster, a suburb of Rochester. Dozens of bouquets were left at the fire station, along with a handwritten sign that said, "Thanks for protecting us. RIP."
Spengler fired at the four firefighters when they arrived shortly after 5:30 a.m. Monday to put out the fire, Pickering said. The first police officer who arrived chased the gunman and exchanged shots.
Authorities said Spengler hadn't done anything to bring himself to their attention since his parole. As a convicted felon, he wasn't allowed to possess weapons. Monroe County District Attorney Sandra Doorley said Spengler led a very quiet life after he got out of prison.
A friend said Spengler hated his sister. Roger Vercruysse lived next door to Spengler and recalled a man who doted on his mother, whose obituary suggested contributions to the West Webster Fire Department.
"He loved his mama to death," said Vercruysse, who last saw his friend about six months ago.
Vercruysse also said Spengler "couldn't stand his sister" and "stayed on one side of the house and she stayed on the other."
The West Webster Fire District learned of the fire after a report of a car and house on fire on Lake Road, on a narrow peninsula where Irondequoit Bay meets Lake Ontario, Monroe County Sheriff Patrick O'Flynn said.
Emergency radio communications capture someone saying he "could see the muzzle flash coming at me" as Spengler carried out his ambush. The audio posted on the website RadioReference.com has someone reporting "firefighters are down" and saying "got to be rifle or shotgun - high powered ... semi or fully auto."
Two of the firefighters arrived on a fire engine and two in their own vehicles, Pickering said. After Spengler fired, one of the wounded men fled, but the other three couldn't because of flying gunfire.
The police officer who exchanged gunfire with Spengler "in all likelihood saved many lives," Pickering said.
A police armored vehicle was used to recover two men, and eventually it removed 33 people from nearby homes, the police chief said. The gunfire initially kept firefighters from battling the blazes.
The dead men were identified as police Lt. Michael Chiapperini, 43, the Webster Police Department's public information officer; and 19-year-old Tomasz Kaczowka, also a 911 dispatcher.
Pickering described Chiapperini as a "lifetime firefighter" with nearly 20 years in the department, and he called Kaczowka a "tremendous young man."
Kaczowka's brother, reached at the family home Monday night, said he didn't want to talk.
The two wounded firefighters, Joseph Hofstetter and Theodore Scardino, were in stable condition Tuesday at Strong Memorial Hospital, the chief said. Both were awake and alert and are expected to recover.
Hofstetter, also a full-timer with the Rochester Fire Department, was hit once in the pelvis, and the bullet lodged in his spine, authorities said. Scardino was hit in the chest and knee.
Cathy Bartlett was at a vigil Monday night with her teenage son, who was good friends with Kaczowka. Bartlett's husband, Mark Bartlett, has been a firefighter there for 25 years but missed the call this morning.
"Thank God my husband slept through the first alarm and didn't get up until the second one went off," she said.
The shooting and fires were in a neighborhood 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.
"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."
Gov. Andrew Cuomo said the State Police and Office of Emergency Management were working with local authorities.
"Volunteer firefighters and police officers were injured and two were taken from us as they once again answered the call of duty," Cuomo said in a statement. "We as the community of New York mourn their loss as now two more families must spend the holidays without their loved ones."
Webster, a middle-class suburb, now is the scene of violence linked to house fires for two Decembers in a row.
Last Dec. 7, authorities say, a 15-year-old boy doused his home with gasoline and set it ablaze, killing his father and two brothers, 16 and 12. His mother and 13-year-old sister escaped with injuries. He is being prosecuted as an adult.
Associated Press writer Mary Esch in Albany contributed to this report.