NEWTOWN, Conn. (AP) -- When Adam Lanza walked out of his house for the last time, he left behind firearms and knives and more than 1,600 rounds of ammunition -- taking only four guns. They would suffice.
He loaded the weapons into his car, drove to Sandy Hook Elementary School, blasted his way into the building and within five minutes fired off 154 shots with a Bushmaster .223-caliber rifle. Having slaughtered 20 first-graders and six educators, he killed himself with a shot from a Glock handgun. He still had more than 100 rifle bullets at hand.
Warrants released Thursday provide the most insight to date into the world of the 20-year-old gunman, a recluse who played violent video games in a house packed with weaponry that was all too real. The inventory of items found in the spacious, colonial-style home included books on autism, a vast array of weapon paraphernalia and images of what appears to be a dead person covered with plastic and blood.
The weapons used in the shooting had all apparently been purchased by Lanza's mother, Nancy, with whom he lived, said prosecutor Stephen J. Sedensky III, in a statement accompanying the warrants.
She was found dead in her bed; Adam Lanza had shot her the morning of the massacre, Dec. 14. Authorities also found a gun safe in his bedroom and a holiday card from Nancy Lanza containing a check made out to her son for the purchase of yet another firearm.
Connecticut Gov. Dannel P. Malloy expressed incredulity over the access that the troubled young man had to a cache of weapons.
"There are parts of this story that are unfathomable," he said. "How anyone would have maintained that household that way is difficult to understand."
Mark Barden, whose 7-year-old son, Daniel, was killed at Sandy Hook, said he was not surprised by anything revealed Thursday.
"Most of this is pretty high level stuff that we were aware of already and it just reminds me of what happened, that a gunman stormed his way into an elementary school and shot to death 26 people, 20 of which were first-grade boys and girls," Barden said.
The shooting elevated gun safety to the top of President Barack Obama's agenda; at an event in Washington on Thursday, joined by the families of four children killed at Sandy Hook, he urged lawmakers not to get "squishy" in the face of opposition to gun control.
"Shame on us if we've forgotten," Obama said. "I haven't forgotten those kids."
The debate has extended to Newtown, a rural community of 27,000 people in western Connecticut that is also home to the National Shooting Sports Foundation. A protest and counter-protest were held outside the foundation's offices Thursday.
If it's possible to determine a motive for the massacre, there may be clues in Adam Lanza's journals, which state police seized from the house and turned over to the FBI for analysis. But authorities say that so far no conclusions have been reached. Sedensky estimated that the investigation will be finished this summer.
At the Lanza house, investigators found books about autism and Asperger's syndrome, as well as one with tabbed pages titled "Train Your Brain to Get Happy." Adam Lanza was said to have been diagnosed with Asperger's, an autism-like disorder that is not associated with violence.
But the warrants also reveal an intense interest in weaponry and violence.
A gun locker in the house was open when police arrived in the aftermath of the shootings, and there was no sign it had been broken into.
Investigators found a 7-foot pole with a blade on one side and a spear on another, a metal bayonet, three samurai swords, a .323-caliber bolt-action rifle, a .22-caliber Savage Mark II rifle and a .22-caliber Volcanic starter pistol. There was a military-style uniform in Lanza's bedroom; literature seized from the house included a news article on a 2008 shooting at Northern Illinois University and a National Rifle Association guide to pistol shooting.
News outlets including The Associated Press reported previously that Lanza showed interest in other mass killings. Some, including The Hartford Courant, reported that he had a particular interest in Norwegian mass murderer Anders Behring Breivik, who killed 77 people in twin attacks in 2011 in Norway's worst peacetime massacre.
In a duffel bag, investigators found ear and eye protection, binoculars, numerous paper targets and an NRA certificate that belonged to Adam Lanza. The NRA said Lanza was not a member.
An unnamed person told investigators that Lanza was an avid gamer who played "Call of Duty" and rarely left his home. The affidavit, which is partially blacked out, also has that person saying that Sandy Hook, the school Lanza attended as a child, was his "life."