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 apparently got hold of at least a few of them to commit a massacre in an elementary school is still unclear.

Authorities believe he killed his mother as she slept in her bed. She was shot four times in the head, Connecticut Chief Medical Examiner H. Wayne Carver said Tuesday.

Then, authorities say, Adam Lanza went to Sandy Hook Elementary -- which he'd once attended -- and killed 20 children and six adults.

Then, he used a handgun to kill himself with a shot to the front of the head, Carver said.

Friend, classmate describe family

A friend of Nancy Lanza, who had done contracting work for her, was last in the home eight months ago and remembers seeing a lock box in the basement where Lanza kept her guns.

He describes her as a country girl from New Hampshire who grew up shooting.

The two of them bonded, partly because both had family members with autism, the friend said.

He also said he met Adam Lanza, who did not make eye contact or engage in conversation.

Lanza tried hard to mainstream her son, the friend said. He now questions whether she tried too hard to have him "fit in."

He says she took her son with her to the gun range because, she said, she couldn't always leave him at home.

On Monday, just a few days after the massacre at the school, a schoolmate of Adam Lanza told CNN that he bumped into Nancy Lanza a while ago.

Alan Diaz, 20, who was a freshman at Newtown High School when Adam Lanza was a sophomore, 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 that 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."