A gunman killed his mother Dec. 14, in their Newtown, Conn., home then drove to nearby Sandy Hook Elementary School, where he opened fire, killing 20 children and six adults before taking his own life.
An investigation into the Newtown school shooting did not determine a motive for the attack that killed 20 children and six women, a prosecutor says, but did reveal that the shooter had an obsession with the 1999 Columbine High shootings and other such mass killings.
State's Attorney Stephen Sedensky III, who led the investigation, said there is no clear indication why 20-year-old Adam Lanza chose Sandy Hook Elementary School as the target for his rampage other than the fact that it was close to his home. The summary report by Sedensky comes nearly a year after the massacre.
He said Lanza had significant mental health issues that affected his ability to live a normal life and interact with others but did not affect his mental state for the crimes.
Sedensky added that police went into the school within minutes of the first shots being fired and that along with the actions of teachers inside saved many children's lives.
"Why did the shooter murder twenty-seven people, including twenty children?" Unfortunately, that question may never be answered conclusively, despite the collection of extensive background information on the shooter through a multitude of
interviews and other sources," investigators said in a long-awaited report released Monday.
To try to figure out the motive, investigators said, they interviewed members of Lanza's family — his father and brother cooperated fully — along with teachers and others. They said they also tried within the limits of privacy laws to gather information on his medical treatment.
They found no evidence he had taken any medication that would have affected his behavior or explain the bloodbath.
Lanza "was under no extreme emotional disturbance for which there was a reasonable explanation or excuse," the report concluded.
It said that in fifth grade, Lanza wrote a book that included tales of children being slaughtered and a son shooting his mother in the head.
The spiral-bound manuscript, "The Big Book of Granny," was among items seized from his home. There is no indication he ever handed in the book at school.
The main character has a gun in her cane and shoots people, and another character likes hurting people, especially children.
In the years that followed, he was obsessed with mass murders, such as the 1999 Columbine High School massacre, assembling articles, photos, books, footage and violent video games, including one in which players gun down students in school. He even kept a spreadsheet ranking mass murders.
The report said that in 2005, Lanza was diagnosed with Asperger's disorder — an autism-like condition that is not associated with violence — and that he lacked empathy for others and behaved strangely. He seemed to have few friends.
Nobody was allowed into his bedroom, not even to clean, according to the report. The windows of the room were covered with black trash bags. The report also said Lanza also disliked birthdays, Christmas and holidays and did not like to have his hair cut.
He also wouldn't touch doorknobs, his food had to be arranged on the plate in a certain way, and he changed clothes and washed his hands often during the day. He was a loner at school and was repelled by crowds and loud noises. His mother got rid of a cat because her son didn't want it in the house.
Weeks before the Newtown shooting, Nancy Lanza was concerned about her son and said that he hadn't gone anywhere in three months and would communicate with her by email only, even though they lived in the same house, according to the report.
However, she never expressed fear that she or anyone else was in danger from Adam, the report said. She was in New Hampshire the week before the shooting, arriving home the evening of Dec. 13.
The next day, the shooting plunged the small New England community into mourning, elevated gun safety to the top of the agenda for President Obama and led states across the country to re-evaluate laws on issues including school safety.
Lanza killed his mother inside their Newtown home before driving to his former elementary school, where he fired off 154 shots with a Bushmaster .223-caliber rifle within five minutes. He killed himself with a handgun as police arrived.
The report released Monday afternoon did not include the full evidence file of Connecticut State Police, which is believed to total thousands of pages and is expected to be released at a later date. The decision to continue withholding the bulk of the evidence is stirring new criticism of the secrecy surrounding the investigation.
Dan Klau, a Hartford attorney who specializes in First Amendment law, said the decision to release a summary report before the full evidence file is a reversal of standard practice and one of the most unusual elements of the investigation.
"What I found troubling about the approach of the state's attorney is that from my perspective, he seems to have forgotten his job is to represent the state of Connecticut," Klau said. "His conduct in many instances has seemed more akin to an attorney in private practice representing Sandy Hook families."
Sedensky said he could not comment, but he has gone to court to fight release of the 911 tapes from the school to spare the victims' families the anguish. A judge said Monday he will listen to the recordings before deciding whether they can be made public.
The withholding of 911 recordings, which are routinely released in other cases, has been the subject of a legal battle between The Associated Press and Sedensky before the state's Freedom of Information Commission, which ruled in favor of the AP, and now Connecticut's court system.
Donna Soto, the mother of slain teacher Victoria Soto, said in a statement that nothing could make sense of the shooting.
"Yes, we have read the report, no, we cannot make sense of why it happened. We don't know if anyone ever will," Soto wrote. "We don't know if we will ever be whole again, we don't know if we will go a day without pain, we don't know if anything will ever make sense again."
Teresa Rousseau, whose daughter Lauren was among the six educators killed at Sandy Hook, said she hasn't read the report.
"It's just too painful to go there," Rousseau said.
The Associated Press contributed to this report.