Monroe County Sheriff's Office via NBC News
Undated booking photo of William Spengler, who shot and killed two firefighters Monday.
WEBSTER, N.Y. -- Officials in Webster, NY held two press conferences Tuesday on the Two Rochester-area Firefighters Shot and Killed Monday - Christmas Eve.
The man who killed two Webster firefighters and critically injured two others was armed with three firearms, including a Bushmaster .223 rifle - the same weapon believed to be used in the massacre at Sandy Hook Elementary School.
In Tuesday afternoon press conference, Police announced that they found human remains, believed to belong to Cheryl Spengler, 67, the shooter's sister, who has been missing since Monday. The Monroe County Medical Examiner's Office will investigate the remains. Police say no one else involved in the shooting is missing.
"Motive is always the burning question," Pickering said. "I'm not sure we'll ever really know what was going through his mind."
At a news conference this morning, Webster Police Chief Gerald Pickering released new details about Monday's ambush.
Armed with the semi-automatic rifle, a shotgun and a .38 caliber handgun, William Spengler Jr. set a "clear ambush" for first responders, Pickering said, and carried out the horrific plan he detailed in a typewritten note he left behind.
Spengler left a note, which Pickering said was two to three pages long, rambling and did not speak to a motive.
Spengler's attack killed firefighters Mike Chiapperini and Tomasz Kaczowka, and severely injured firefighters Joseph Hofstetter, 33, and Theodore Scardino, 48, who are in stable condition at Strong Memorial Hospital. An off-duty Greece police officer, John Ritter, was injured by shrapnel while attempting to protect the wounded officers with his car. He was treated and has been released from an area hospital. Pickering described his actions as heroic.
Pickering said it was not yet known which weapon was used to shoot the four firefighters.
Once police arrived at the scene, "it was a combat condition," Pickering said.
"We're assuming it was the rifle, because of the distance." That rifle, he said, was equipped with a flash suppressor, intended to reduce the visibility of a shooter during firing.
Lake Road remains closed to traffic between Bay Road and the bay bridge, though many residents are being allowed back into their homes and power has been largely restored. The area between 169 and 213 Lake Road remains cordoned off entirely, and is considered an active crime scene, Pickering said.
Investigators are "sorting through the rubble" of the seven houses destroyed by fire, and firefighters are extinguishing hotspots at two homes today.
Pickering cautioned that people returning to their homes after being evacuated by SWAT teams yesterday may find that their doors were kicked in. Locked homes in the area were searched for suspects during the chaos Monday.
The West Webster Fire Department is taking donations to assist the families of the four firefighters.
WGRZ/Rochester Democrat and Chronicle