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 and Ryan Lanza were questioned after Friday's rampage.
CNN spoke with a friend of Nancy Lanza who said she'd grown concerned about Adam lately, worrying about what she was going to do with her boy who was growing up, maybe in the way that all mothers worry.
She talked about wanting to sell her house and move West, and was eyeing Washington state. Lanza wasn't debilitated, though, by her worry. She still got out there and lived. She went on short vacations and went to Red Sox games.
The friend asked not to be named.
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.