Adam Lanza, 20, was the shooter behind Friday's massacre at the Sandy Hook Elementary School in Newtown, Connecticut.
He shot and killed 26 people at the school, including 20 young children, before shooting himself dead.
Here's what we know about him.
1. People Believed Adam Lanza Was A Time Bomb
According to the Daily News a family insider said of Adam Lanza, "This was a deeply disturbed kid. He certainly had major issues. He was subject to outbursts from what I recall."
Classmates and family friends recall him as weird and quiet, but smart and disturbed. When it was wrongly reported that his older brother Ryan Lanza was the shooter, a former neighbor knew immediately that it had to be Adam.
He also might not have been able to feel pain. A longtime family friend told the Daily News, "A few years ago when he was on the baseball team, everyone had to be careful that he didn't fall because he could get hurt and not feel it. Adam had a lot of mental problems.
2. He Had Asperger's Syndrome
Brother of gunman tells authorities his younger brother is autistic, or has Asperger syndrome & a personality disorder abcn.ws/UMG79i
— ABC News (@ABC) December 14, 2012
Adam's brother and high school say he had Asperger's, a high-functioning form of autism. It is not normally tied to violent behavior.
3. His Shot His Mom in the Face at Home
— CBS News (@CBSNews) December 14, 2012
Adam Lanza began his killing spree at home, shooting his mother in the face before driving to the school in her car. Early reports erroneously said the killer's mom was a teacher killed at the school during the massacre, but her body was found at her Newtown home. Her death brings the day's toll to 28.
4. His Dad is NOT Dead
Despite earlier reports, Adam's father Peter Lanza is alive, according to the Stamford Advocate — which describes his reaction when a reporter told him the news:
When he was told his address had been linked to the Newtown school shooting, Lanza took the news as a blow — his face turning from patient to surprised and horrified.
5. He Lived With His Mother
He had been living with his mother in the family’s four-bedroom, 3,100-square-foot estate where he killed her before he went on a shooting spree at her former school. His parents divorced in 2008 and his father Peter is now living in Stamford, CT, with his second wife.
His mother was very worried of his mental state and extremely protective of him.
6. He Used His Mom's Guns
UPDATE: Weapons used in shooting were legally purchased and registered to gunman's mother, law enforcement officials tell NBC News
— NBC News (@NBCNews) December 14, 2012
Adam wielded his mom's .223 caliber assault rifle to shoot his way into the school and kill 26 people. He then shot himself dead with one of two handguns he was carrying. The weapons were reportedly legally purchased — registered to Adam's mother, Nancy. He fired at least 100 rounds and had hundreds more unspent rounds with him in high-capacity magazines — enough ammo to kill everyone in the school. Nancy was reportedly and avid gun collector and took her sons shooting. She was passionate about guns.
— Andrew Kaczynski (@BuzzFeedAndrew) December 14, 2012
7. His Brother, Ryan Lanza, Was Questioned by Police
Ryan Lanza, the 24-year-old older brother of Adam, lives in Hoboken, New Jersey. Police now believe Ryan was not involved and that Adam worked alone.
8. Adam Was Carrying Ryan's ID
Ryan, not Adam, was first widely reported as the killer. Ryan's Facebook photo was distributed far and wide by numerous major media outlets. The confusion arose because Adam was carrying Ryan's identification.
9. We're Still Not Sure Why He Did It
Other than being disturbed, we have very little knowledge about why Adam Lanza killed his mother and so many children. Police are looking into it and seem to have found some writings in his home that give them some idea, but they are refusing to release any information until they can confirm it. So much false information has already swirled about this tragedy.
10. There Have Been A Lot Of False Reports
Right now, the information regarding Adam Lanza and the Sandy Hook Massacre is very fluid. More information keeps coming in and it then frequently turns out to be wrong. So to clarify:
The shooter was Adam Lanza, not Ryan Lanza his brother as was originally reported.
Peter Lanza, Adam Lanza's father, is not dead and has not been killed by Adam.
Nancy Lanza, Adam Lanza's mother, was found in the home she shared with Adam, not the school as previously reported. She did not work for Sandy Hook Elementary. She did have a connection to the school that law enforcement is aware of, but is currently now publicly known.
There have been reports of Adam Lanza attempting to buy a gun the day before the attack, but there has been no evidence found of this.
Adam Lanza did not get into an altercation with school officials two days before the massacre.
He, in fact, used the .223 inside the school to commit the massacre, it was not found in his trunk.
He did not drive up from New Jersey to commit the attack.
The number of victims has fluctuated. The final count is 28 dead, 20 of which were children aged 6 and 7.
Nearly every rumor floating around since the attack has been debunked.