William Spengler killed two firefighters and
William Spengler killed two firefighters andReuters

The man who carried out a grisly murder plot on Monday, ambushing volunteer firefighters in upstate New York, killing two and wounding two, left behind a chilling note, revealing his dark, sinister intentions. 

The three-page note, left by William Spengler, 62, who used a Bushmaster semiautomatic rifle to carry out his attack, the same kind of weapon used in the tragic murder of 27 people at Sandy Hook Elementary School, revealed that the deranged criminal hoped to burn down his neighborhood and kill as many people as possible.

Spengler, who was convicted of killing his grandmother decades ago, was found dead hours later, an apparent suicide.

At a news conference Tuesday, Webster Police Chief Gerald Pickering read a sentence from the typewritten note, which stated, "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."

Pickering would not reveal the entire contents of the note, which will not be made public because it is evidence in a criminal investigation, he said.

The note gave a bit of clarity as to what Spengler wanted to do, but the why remains unclear, specifically why Spengler chose to target volunteer firefighters. 

Just before 6 a.m. Monday, firefighters from the town of Webster responded to a 911 call reporting a fire that Spengler is believed to have set, and shortly after the gunfire began.

"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 to be nearby, returned gunfire and used his car to shelter firefighters.

"Had the police officer not been there, more people would have been killed because he immediately engaged the shooter with a rifle," Pickering said. "Essentially, it was a combat condition." Investigators won't know until after an autopsy if any of his shots hit Spengler, he said.