NEWTOWN, CT (CNN) -- Nancy Lanza was raising a quiet, socially awkward young man, the kind of teenager who, a former classmate recalled, would just go stand in the corner.
Lanza herself seemed nothing like her boy. She was affable and outgoing, and easily made friends.
Sure, she liked guns, say people who knew her. But she was responsible with them. She knew how to handle the weapons she collected.
How Adam Lanza allegedly got hold of at least a few of them to commit a massacre in an elementary school is still unclear.
Authorities believe he shot his mother as she slept in her bed. Then, authorities say, Adam Lanza went to Sandy Hook Elementary -- where he'd once attended -- and mowed down 20 children and six adults.
Then, authorities say, he killed himself.
On Monday, just a few days after that horror, a former classmate of Adam Lanza told CNN that he bumped into Nancy Lanza awhile ago.
Alan Diaz, 20, asked her how her son was doing.
To Diaz, it seemed that Adam Lanza just disappeared from high school after his sophomore year, but it turns out Lanza, then 16, was taking classes at Western Connecticut State University, a school spokesman said.
It was hard to forget a kid like Adam Lanza.
"I would call him a genius," Diaz said.
Lanza got a 3.26 GPA at WCSU, including an A in a computer class, the school spokesman told CNN, but Lanza took his last class in 2009 and didn't come back.
When Diaz and Lanza were classmates, Diaz went out of his way to include Adam Lanza when few others would, he said.
It worked, for a little while.
Lanza opened up, sometimes telling jokes to the other students. There he'd be, in the same plaid green button-up shirt and his khakis -- the weird kid, telling jokes.
So those few years later, seeing Adam Lanza's mother, Diaz just had to ask. How are things going with Adam?
"When I talked to Nancy that time, about how he was doing, she said he's been going to the (gun) range a lot recently," Diaz told CNN. "That he'd taken that up as a hobby."
Guns and Gardening
Nancy Lanza was a personable neighbor, acquaintances said. Sandy Hook is an affluent area about 60 miles from New York City.
The homes are huge and so are the yards.
It's the kind of neighborhood where Christmas cookies are exchanged and people get together at each others' houses.
When Connecticut winters bring blankets of snow, the kids ride sleds on a big hill in the neighborhood.
Nancy Lanza and her two boys -- Ryan and Adam -- and her husband, Peter, moved there around 1998.
The couple divorced in 2009. Peter Lanza is listed on LinkedIn, as a tax director and vice president of taxes for GE Energy Financial Services in the New York City area. According to divorce documents, he agreed to pay his wife, on average, $250,000 a year in alimony. He also agreed to buy his son Adam a car, though his wife would have to pay for the vehicle's upkeep and insurance.
Adam Lanza's primary residence was with his mother, the documents show. They lived in the Newtown home that Peter Lanza ceded to Nancy.
The father was also responsible for paying for Adam's college, as well as for Ryan Lanza's schooling.
Peter Lanza and his other son, Ryan, were both questioned after Friday's rampage.
A 'normal' family and target shooting
"It was just a nice, normal family," neighbor Rhonda Cullen said Saturday, recalling how she and other women on the street would often go to each others' houses to play cards.
Nancy Lanza preferred to garden.
"We used to joke with her that she'd do all this landscaping that no one could see because it all was in the back (of the house)," Cullen said.
Nancy Lanza was also into collecting guns, say those who know her.
Dan Holmes, who owns a local landscaping business, said she showed off a rifle she recently purchased.
"She told me she'd go target shooting with her boys pretty often," Holmes said.
Nancy Lanza kept a lot of weapons, from assault rifles to handguns, at her home.
The weapons were for self-defense, said Marsha Lanza, Peter Lanza's sister.
Yet, Marsha Lanza said her former sister-in-law "never felt threatened." If she did, Marsha Lanza said, Nancy would have spoken up about it.
Nancy was self-reliant, a trait that she possibly picked up while growing up on a farm in New Hampshire, Marsha Lanza said.
At some point, she worked in finance in Boston and Connecticut, a friend said.
She was not a teacher, as some media had previously reported, the friend added.
Despite whatever problems Nancy Lanza might have been facing behind closed doors, on the outside she kept a cheerful face. Several people who knew Nancy Lanza said she was incredibly social and warm.
Several nights a week, she got take-out from My Place bar in Newtown.
CNN sat down with owners Louise Tambascio, Mark Tambascio and John Tambascio.
Louise recalled Nancy starting a conversation with her, and how they become fast friends.
"She's funny. We took to her," said Mark Tambascio. "She did a lot in town and was always on the go."
Louise Tambascio said Nancy Lanza worked in charities for people with AIDS, and said she was extremely generous.
Louise saw Nancy Lanza take out her checkbook and write checks to anyone who told her they were going through a rough time and needed money.
"She was very kind," Louise said.
Lanza was generally in a good mood, several people said.
"Every time I saw her she was so giddy and happy," said Amanda D'Ambrose, 23, Alan Diaz's sister.
D'Ambrose also knew Adam, and knew that Nancy owned guns.
"She was very responsible. She transported them safely. It wasn't something she boasted about," D'Ambrose told CNN.
Yet when she heard the news that there had been a shooting at Sandy Hook Elementary, D'Ambrose started calling Nancy Lanza's cell phone.
As the young woman recalls this terrible moment, she weeps. I was "hoping it wasn't true," she said.
Guns of the mother
The three weapons found at the scene of the shooting were legally purchased by Nancy Lanza, a law enforcement official familiar with the investigation told CNN.
The Bureau of Alcohol, Tobacco and Firearms is investigating the school shooting.
CNN confirmed Monday afternoon with ATF that Adam Lanza and his mother frequented several gun ranges over the past several years. The agency will not identify which ranges.
Police Chief Donald Briggs Jr. said he, too, knew Nancy Lanza.
"She was a great person who would do anything for you, a heart of gold," he told the Union Leader newspaper.
"She was just a real, real nice, nice person."
Alan Diaz keeps asking the same question everyone is. How could this person he knew, who seemed a little off, kill children?
"You know," he began. "In the media the person who does (these) things is seen as just evil. But I've thought for a long time, What about the people who knew them? What about the friends?"
He chews this over.
"They knew them as a person. And now, being in that situation, it is very strange," Diaz said. "I knew this kid and there was no sign ever that he could hurt another person.
So many people told Alan Diaz not to talk to reporters, but he just wants to talk. He wants information he might never get.
"I want to know how this could happen. How ... a shy kid could do this."
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