Before William Spengler opened fire on firefighters who had arrived to put out a fire at his home in the upstate New York town of Webster, killing two and seriously wounding two others, he typed a couple of pages announcing his plans.
"I still have to get ready to see how much of the neighbourhood I can burn down and do what I do best: killing people," Spengler wrote, police said.
The previous morning, Spengler shattered the holiday calm with an assault that officials found uncharacteristic of the 14 years he had spent out of prison since killing his grandmother with a hammer in 1980.
Monday's fire destroyed seven homes and damaged two more in Webster, a suburb of Rochester. Officials also said they found remains at Spengler's house that they suspect were those of his sister, Cheryl, 67.
Police think Spengler, 52, used a Bushmaster .223-calibre rifle with a flash suppressor in his rampage. They recovered the weapon along with a Smith and Wesson .38-calibre revolver and a Mossberg pump-action 12-gauge shotgun.
Officials were not sure how Spengler, a felon who was not allowed to own guns, had obtained his weapons, but said he was armed to the teeth.
"He was equipped to go to war and kill innocent people," Webster's police chief, Gerald Pickering, said.
One of the men killed a day earlier was Mike Chiapperini, 43, a Webster police lieutenant as well as a volunteer firefighter.
Spengler's attack was the third time in two weeks that a shooter has killed multiple victims with an assault rifle.
On December 14, Adam Lanza, 20, killed 20 grade-school children and six adults at Sandy Hook Elementary School in Newtown, Connecticut, using a military-style Bushmaster .223-calibre rifle. Lanza also killed his mother and himself. And on December 11, Jacob Tyler Roberts opened fire in a mall in Clackamas, Oregon, with an AR-15-style rifle, killing two and wounding one before killing himself.
Spengler, who also shot himself, is the only one of the three known to have left a note. Police characterised it as "rambling" and said he did not express a motive. They declined to release more excerpts.
"Motive is always the burning question, and I'm not sure we'll ever really know what was going through his mind," Pickering said.
A friend of the gunman said Spengler hated his sister and loved his mother, who had lived with the pair until she died on October 7.
The fire began next door to the home where Spengler had killed his 92-year-old grandmother, for which he served 18 years in prison. He was released in 1998.
Officials on Tuesday described a chaotic "combat situation".
A Webster police officer used his duty rifle to trade fire with Spengler on Monday in morning darkness after the firefighters had been fired upon before getting out of their trucks, police said.
Rounds shattered the windshield of the fire engine that two of the firefighters were in; the wounded driver crashed it into a bank trying to get away.
"Had that police officer not been there, more people would have been killed, because he immediately engaged the shooter," Pickering said of his officer.
Police officer Jon Ritter was driving behind the fire engine when he also came under fire. He was wounded when bullets struck his windshield and engine block.
Ritter "tried to shelter some of the fallen firemen with his car when the other firefighters, that we later extracted from the location with the armoured personnel carrier, had taken cover under the fire engine to try to escape further harm from the ongoing gunfire," Pickering said.
The two wounded firefighters remained in intensive care.