An ex-con killed two firefighters with the same caliber and make military-style rifle used in the Connecticut school massacre after typing a note pledging to burn down his neighborhood and “do what I like doing best, killing people,” police said Tuesday as another body, believed to be the gunman’s missing sister, was found.

William Spengler, 62, who served 17 years in prison for manslaughter in the 1980 hammer slaying of his grandmother, set his house afire before dawn Christmas Eve before taking a revolver, a shotgun and a semiautomatic rifle to a sniper position outside, Police Chief Gerald Pickering said.

The death toll rose to three as police revealed that a body believed to be the killer’s 67-year-old sister, Cheryl Spengler, was found in his fire-ravaged home.

Authorities say he sprayed bullets at the first responders, killing two firefighters and injuring two others who remained hospitalized Tuesday in stable condition, awake and alert and expected to survive. He then killed himself as seven houses burned on a sliver of land along Lake Ontario.

Police recovered 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., that killed 26, including 20 young children, Pickering said.