Shooter who ambushed firefighters left note showing intent to burn, kill The shooter used a Bushmaster rifle, the same kind used in the Sandy Hook assault, police say Two wounded firefighters are in stable condition after surgery William Spengler, 62, shot himself to death after his ambush killed two firefighters, police say Spengler was convicted in 1981 of killing his grandmother (CNN) -- A sniper who ambushed volunteer firefighters in upstate New York on Monday, killing two and seriously wounding two others, left a note saying he hoped to burn down his neighborhood and kill as many people as possible, police said Tuesday. William Spengler, 62, used a Bushmaster semiautomatic rifle, the same kind of weapon used in the assault on Sandy Hook Elementary School, Webster Police Chief Gerald Pickering said. The shooter, who was convicted of killing his grandmother decades ago, was found dead of a self-inflicted gunshot wound hours later. Chief Pickering, at a news conference Tuesday, read a sentence from the three-page typewritten note that detectives believe Spengler's left behind: "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." The note indicated Spengler's intentions, but not his motive, Pickering said. The rest of the contents will not be made public because it is evidence in a criminal investigation, he said. There is "all kinds of speculation" about why Spengler wanted to destroy his neighborhood and kill firefighters and residents, Pickering said. One theory is that he was upset about a donation his mother, who died in the past year, made to the fire department, he said. Another theory is there could be a connection to his arrest in the killing of his grandmother, he said. Spengler was convicted in 1981 of first-degree manslaughter in the death of his grandmother and had been released on supervised parole, Pickering said. Investigators have been unable to find Spengler's sister, who lived in the home with him, Pickering said. Firefighters from the Rochester-area town of Webster responded before 6 a.m. to a 911 call, reporting a fire that Spengler is believed to have set, when the gunfire began, he said. "This was a clear ambush on first responders," Pickering said. Spengler was firing from "a natural depression" against a bank and a tree, he said. An off-duty police officer, who happened on the scene, returned gunfire and sheltered firefighters with his car, Pickering said. "Had the police officer not been there, more people would have been killed because he immediately engaged the shooter with a rifle," he said. Essentially, it was a combat condition. Investigators won't know until after an autopsy if any of his shots hit Spengler, he said. Officer John Ritter of the Greece, New York, Police Department, suffered minor shrapnel wounds but was released after treatment at a hospital. The two wounded firefighters were in stable condition after surgery Tuesday, Pickering said Tuesday morning. They are being treated for "serious injuries" in intensive care at Strong Memorial Hospital in Rochester, New York, he said. Seven houses were destroyed and several others damaged by the fire, which investigators believe spread from a car parked next to the home where they believe Spengler lived, Pickering said. Authorities do not know how Spengler obtained the Bushmaster rifle, .38-caliber revolver and 12-gauge shotgun he used, Pickering said. As a convicted felon, Spengler was not allowed to legally possess weapons. In chilling audio heard over a scanner Monday, a West Webster Fire Department firefighter reported "multiple firemen shot" -- including himself, with wounds to his lower back and lower leg -- and "shots still being fired." "I'm pretty sure that we have two DOAs" -- the term for dead on arrival -- "on the street," the wounded firefighter said. ..." They're down and not good. For several hours after that, the threat of gunfire stopped firefighters from battling the blaze and forced police SWAT teams to evacuate 33 people in the neighborhood of small waterfront homes. The fire destroyed seven houses. It was under control by 2:30 p.m. ET, but authorities weren't able to get into any of the homes. Pickering said it's possible that more victims could be inside. Lt. Michael Chiapperini, a firefighter who died at the scene, was a veteran of the West Webster Fire Department and a police lieutenant. He'd been named Firefighter of the Year just two weeks ago. And not long before that, he had volunteered to go to Long Island to help those suffering after Superstorm Sandy, New York Lt. Gov. Bob Duffy said. The other slain firefighter was Tomasz Kaczowka, who was also a 911 dispatcher. He'd been with the West Webster Fire Department for just more than a year, department spokesman Al Sienkiewicz said.