The upstate man who set his house on fire then shot firefighters as they arrived to extinguish the blaze is suspected of also killing his sister. Cheryl Spengler, the 67-year-old sister of 62-year-old William Spengler, is missing, but investigators believe that remains found inside the Webster, NY home will prove to be her. Neighbors say William Spengler hated his sister—they shared the lakefront house together, but lived on opposite sides.

"He loved his mama to death," one neighbor told NBC. But Spengler "couldn't stand his sister" and "stayed on one side of the house and she stayed on the other." Spengler's mother, who had also resided in the home, passed away in October, apparently of natural causes. But Spengler really loved his grandmother "to death"—he killed her with a hammer in 1980. After serving 17 years in prison for manslaughter, he moved back to the house on the lake.

Investigators have not yet confirmed that the remains found in the house were Spengler's sister because the body was too burned to immediately identify, and it's unclear if she died from the fire or at her brother's hand. "It was a raging inferno in there," Police Chief Gerald Pickering told reporters yesterday. Police also found a 2-3 page "rambling" note from Spengler. Pickering declined to provide it to the media, but he read one line out loud during the press conference: "I still have to get ready to see how much of the neighborhood I can burn down and do what I like to do best—killing people."

Seven houses burned during the incident because Spengler's shooting spree prevented firefighters from safely fighting the blaze. "He was equipped to go to war, kill innocent people," Pickering told reporters. Hiding behind a berm, Spengler fired at firefighters, killing Police Lt. Mike Chiapperini, 43, and Tomasz Kaczowka, 19. Fellow volunteer firefighters were hit—Joseph Hofstetter in the pelvis and spine and Theodore Scardino in the chest and knee. Both are in stable condition and expected to recover.

Spengler, who used a .223 Bushmaster rifle—the same semi-automatic used in the Newtown, Connecticut elementary school massacre—was not allowed to own the firearms used in the attack because of his parole. Police say he also had a shotgun and revolver, which he used to take his own life. "I'm not sure we'll ever know what was going through his mind," Pickering said.