In the aftermath of Friday's elementary school shooting, a shattered New England town searched for clues to why a young man would commit so heinous an act.
The life of Adam Lanza will be dissected, analyzed and re-analyzed in the days to come as investigators dig into the background of the 20-year-old, who law enforcement sources say returned to his elementary school and opened fire.
Thus far, there are clues, but no answers.
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Police have not even publicly confirmed Lanza as the assailant who killed 20 young children between the ages of 5 and 10, plus six adults and himself at Sandy Hook Elementary School in Newtown, Connecticut.
Another adult was found dead at a nearby home, bringing the death toll to 28, but police would not confirm or deny media reports that the person was Lanza's mother, Nancy.
Lanza was a shy and unusually intelligent student, two former classmates recall.
In Newtown High School, he dressed more formally than other students, often wearing khaki pants, button-down shirts and at times, a pocket protector, said Tim Arnone who first met Lanza at Sandy Hook.
Flags surrounding Washington Monument lowered to half-staff (Photo: AFP)
The two of them joined the high school's audio-visual club, also known as a tech club, and spent free periods playing video games at the school's television station studio.
"It was definitely the nerdiest club in the school. We called it the tech club. We had our own little section in the room," Arnone, 20, told Reuters.
He said Lanza was "driven hard" to succeed academically by his parents, particularly his mother. "She pushed him really hard to be smarter and work harder in school," Arnone said.
'My brother may have had personality disorder.' Adam's older brother Ryan
Nancy Lanza and her husband, Peter Lanza, divorced in 2008, according to public records. Peter Lanza could not immediately be reached for comment.
Ryan Kraft, 25, who was a neighbor of the Lanza family, told the Washington Post that the divorce hit the children hard.
"The kids seemed really depressed” by the breakup, Kraft (25) said of the Lanza brothers.
Kraft told The Washington Post that when Nancy Lanza would go out to dinner with friends, she sometimes relied on him to watch Adam Lanza, who was too boisterous for Ryan Lanza to manage. "He would have tantrums," Kraft said. "They were much more than the average kid (had)." However, Kraft said, he was not prone to violence.
Another former neighbor said Adam Lanza was on medication. According to a law enforcement official, a family member told investigators that he had a form of autism.
'Very polite.' Adan Lanza (Archive photo: AFP)
Ryan Lanza told police that his brother apparently suffered from a personality disorder. He said he had not been in touch with his brother since about 2010.
Dan Holmes, owner of a landscaping firm, described Nancy Lanza as an avid gun collector who once showed him a "high-end rifle" that she had purchased.
"She said she would often go target shooting with her kids," he said.
Holmes said he had just last week decorated her yard with Christmas garlands and lights.
She was "very nice, very pleasant and always very appreciative of our work," Holmes said.
Police have not said what weapon or weapons were used in the school killings.
A second former classmate, who declined to be identified, described Lanza as smart but without many friends.
He said he met Lanza when both boys joined the local Boy Scout troop. At that time, he said Lanza was a big fan of Japanese culture, collecting Pokemon cards and playing the PlayStation video game Dynasty Warriors, a weapons-based animated fighting game released in the late 1990s.
"He was a very quiet kid," the friend said. "I remember being his only friend in elementary school. He was always a really nice kid, very polite."
A man who knew Lanza in high school told the Washington Post that "He always seemed like a quiet type. He was never really sociable. When you try to communicate with him, he would just kind of like have one- or two-word responses.
"He was a wicked smart kid, he excelled in everything," the man said. "He graduated high school three years early."
AP contributed to the report