Jansing & Co. , 3/28/13, 9:58 AM ET

FBI interview: Lanza rarely left home, was ‘shut-in’

NBC’s Michael Isikoff shares the newly released details on the investigation of Newtown shooter Adam Lanza and what police found in his home and car.

Inside Newtown gunman Adam Lanza’s 155-bullet shooting spree

Updated
By Tom Winter and Erin McClam

Adam Lanza fired 155 bullets in less than five minutes on the day he killed 20 children and six adults at Sandy Hook Elementary School, the chief prosecutor investigating the massacre said Thursday.

The total included 154 fired from a Bushmaster .223-model rifle and a final bullet, fired from a Glock 10mm handgun, that Lanza used to take his own life, said Stephen Sedensky, the chief prosecutor investigating the shooting.

Three Samurai swords were recovered from the Newtown, Conn., home that Lanza shared with his mother, authorities said as they released search warrants from the second-worst school shooting in American history.

Also recovered were a National Rifle Association certificate, seven of Lanza’s journals, drawings that he made and books, including an NRA guide to the basics of pistol shooting, authorities said. The NRA did not immediately respond to a request for comment.

Other books included “Look Me in the Eye: My Life with Asperger’s” and “Born on a Blue Day: Inside the Mind of an Autistic Savant.”

Among the other items seized were a holiday card containing a check from his mother to buy a firearm, an article from The New York Times about a 2008 school shooting at Northern Illinois University and three photographs of what appeared to be a dead person covered with plastic and blood.

An FBI report included in the search warrants said that Lanza rarely left home, considered himself a shut-in and was an avid gamer who played “Call of Duty,” a first-person shooter game. The home had a safe holding at least four guns, and Lanza considered Sandy Hook Elementary School his “life,” the papers said.

Police recovered nine 30-round magazines for the Bushmaster that Lanza took to the school. Three of the magazines had a full 30 rounds still in them.

On Wednesday, a judge granted a request from prosecutors to withhold some information in the records, including a witness name, credit card information, telephone numbers and serial numbers.

Authorities say Lanza, 20, shot his mother to death at their home on the morning of Dec. 14, then drove to the school and killed 20 first-graders and six teachers and staff before taking his own life.

Among school shootings in the United States, the death toll is second only to the 32 people killed at Virginia Tech in 2007.

Lanza used a Bushmaster .223-caliber XM15-E2S rifle with a 30-round magazine to shoot the victims at the school, authorities have said.

Authorities also found the Glock 10mm semiautomatic pistol and a Sig-Sauer 9mm semiautomatic pistol in the school, one of which Lanza used to kill himself. In the car outside, police found a shotgun.

All those weapons were legally owned by the mother, Nancy Lanza, authorities have said.

There have been reports that Lanza was obsessed with other mass killers, including Anders Breivik, who killed 77 people in a shooting and bomb attack in Norway two years ago.

A law enforcement official told NBC News last month that Lanza had collected material on previous mass shootings, although the source said there was no indication that it played a role in the school massacre.

Police told NBC News in February that investigators were still a long way from determining Lanza’s motive. Police said then that they hoped to have a report on the shooting finished by June.

This article originally appeared on NBCnews.com.

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Inside Newtown gunman Adam Lanza's 155-bullet shooting spree

Updated