[Updated at 3:55 p.m. ET]

NEWTOWN, Conn.—Police investigating the school massacre here seized a sizable arsenal of firearms, knives and samurai swords along with medical records and computer equipment from the 20-year-old gunman's home in the days after the shootings, court documents released on Thursday reveal.

Also on Thursday, Connecticut State Attorney Stephen J. Sedensky III, who's overseeing the case, said Adam Lanza killed 26 people within five minutes of storming into Sandy Hook Elementary School before turning a gun on himself.

The documents—50 pages of affidavits and evidence logs that include a list of items seized from the car and Newtown home Lanza shared with his mother, Nancy—paint a chilling picture of a killer who had been stockpiling weapons in the weeks and months leading up to the Dec. 14 massacre.

[Related: Newtown families appear in Bloomberg anti-gun ads]

But they do little to establish a motive for Lanza, who shot and killed his mother at their home before driving to the school, where he forced his way in and opened fire.

"This is an active, ongoing investigation," Sedensky said in a statement. "No conclusions have been reached, and no final determinations have been made."

Lanza killed all 26 school victims with a Bushmaster .223-caliber model XM15 rifle for which he had 10 magazines capable of carrying 30 rounds each. Sedensky's report says officers recovered 154 spent casings and 58 unfired rounds for the assault-style rifle from inside the school.

Lanza was also armed with a Glock 10 mm handgun, a 9 mm Sig Sauer P226 handgun and additional ammunition for both. Inside the car Lanza drove to the school, police found a 12-gauge shotgun and two magazines containing 70 rounds of ammunition. Lanza took his own life with the Glock as police were arriving at the school, the report states.

According to the unsealed documents, investigators found an empty box for "Battle Tested" vest accessories and hundreds of rounds of various gun ammunition inside the two-story Lanza home.

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Among the other items seized (as detailed by police):

Item #71 - Receipts and emails documenting firearm/ammunition and shooting supplies.

Item #77 - Blue folder labeled "Guns" containing receipts, paperwork, and other firearm-related paperwork.

Item #81 - Paperwork titled, "Conncticut Gun Exchange, Glock 20SF 10mm FS 15 round FC," dated 12/21/11.

Item #83 - Email re: Gunbroker.com dated 10-12-11.

Item #85 - Printed photographs, miscellaneous handwritten papers, and Sandy Hook report card for Adam Lanza.

Item #86 - "Look Me in the Eye—My life with Asbergers" book, "Born on a Blue day—Inside the Mind of an Autistic Savant" book, "NRA Guide to the Basics of Pistol Shooting" book. Exhibit # 605 - One (1) receipt for Timstar Shooting Range located in Weatherford, Ok and one (1) NRA certificate for Nancy Lanza. Exhibit #606 - One (1) Paperback book titled "Train Your Brain To Get Happy," with pages tabbed off. Exhibit #608 - Three (3) photographs with images of what appears to be a deceased human covered in plastic and what appears to be blood. Exhibit #609 - Seven (7) journals and miscellaneous drawings authored by Adam Lanza. Exhibit #612 - One (1) holiday card containing a Bank of America check #462 made out to Adam Lanza for the purchase of a C183 (Firearm), authored by Nancy Lanza. Exhibit #630 - One (1) New York Times article on 02/18/08 of a school shooting at Northern Illinois University.

In addition to several guns and swords found inside the home, police also recovered a long pole with a blade on one side and a spear on the other.

The NRA on Thursday denied any association with the Lanza family, despite the NRA-related items police reported they found in the house.

"There is no record of a member relationship between Newtown killer Adam Lanza, nor between Nancy Lanza ... with the National Rifle Association," spokesman Andrew Arulanandam wrote in a statement. "[Any] reporting to the contrary is reckless, false and defamatory."

Also according to the documents released on Thursday, FBI agents interviewed an unidentified resident who described Adam Lanza as a "shut in" and "avid gamer who plays Call of Duty" and rarely leaves the house. The witness said Lanza had a "gun safe containing at least four guns." Lanza had attended Sandy Hook Elementary School, the person told the FBI, and "that the school was Adam Lanza's 'life.'"

Superior Court Judge John Blawie ordered parts of the documents redacted after state prosecutors requested that the identity of a key witness not be revealed for another 90 days. The judge also approved blacking out some phone, credit card and serial numbers of some of the property confiscated from the Lanza home.

Connecticut State Police briefed family members of the Newtown shooting victims on Wednesday on what was recovered inside the Lanza home and car. About 50 family members attended the meeting, according to the Connecticut Post.

Thursday's release came after state lawmakers, media and Newtown residents criticized police officials for leaking details of their investigation at a convention of police chiefs in New Orleans in March. The details were then published by the New York Daily News.

[Related: The drive from Lanza’s house to Sandy Hook Elementary School]

"If state police officers can leak details of the Newtown investigation at conventions, surely that information can be shared with the Connecticut public," the Hartford Courant wrote in a recent editorial. "It has more of a right to know than out-of-state police chiefs do. ... This isn't information to be hoarded and shared only at the state police water cooler. The longer information is kept under wraps, the more questions there will be about why. Most important, the details will inform the debate about gun control, mental health and violence in society. There's no reason to fear an informed public."

Connecticut's General Assembly has been considering gun-control legislation in the wake of the Newtown shootings, including a ban on assault weapons and high-capacity ammunition magazines. State lawmakers said on Monday they would delay a vote on gun control until after search warrants related to the school shootings were unsealed.

The final police report on the massacre is not expected to be finished until June at the earliest.

Outside the Lanza home on Thursday morning, the police tape that once surrounded it for months was gone, but a Christmas wreath remained hung above the front door. A single news van was parked nearby.

Around 11 a.m., a bus carrying the Columbine (Colo.) High School boys lacrosse team arrived at the entrance to Sandy Hook Elementary School. The driver explained that the team—which is competing at a tournament in southern New York state this week—wanted to pay its respects to the school shooting victims.

The school has remained closed since the shootings.

Sickles reported from Dallas.