Adam Lanza lived among guns.

His mother, Nancy, collected them. She showed them off to her landscaper.

“Guns were her hobby,” said Dan Holmes, the landscaper of Nancy Lanza’s sprawling yard here on the edge of town. “She told me she liked the single-mindedness of shooting.”

Holmes said she even spoke of taking her son to the firing range to practice his aim.

As details of her son’s troubled life trickled out Saturday, the day after he gunned down 20 children and six adults at Sandy Hook Elementary School and his mother at their home, the portrait emerging is one of a detached killer who knew his way around a trigger and of a family that feared outsiders in the home.

Holmes said Nancy Lanza, who was divorced and had reportedly worked in finance, never invited him inside. She would pay him in the yard. The landscaper never laid eyes on Adam Lanza, a skinny, withdrawn, socially awkward 20-year-old who excelled in academics but apparently not in forming deep friendships.

“I would ring the bell on the front door, and she would come out the side and meet me,” he said. “It was a little weird. It’s stranger now thinking back on what happened.”

When she wanted to show Holmes an antique rifle, she proudly brought the gun — in its case — outside. How many guns Nancy had is not clear, though authorities say several were registered to her, including the ones used in the massacre.

Her former sister-in law, Marsha Lanza, told the Chicago Sun-Times outside her home in Crystal Lake, Ill., that Nancy Lanza wanted guns for protection. “She prepared for the worst,” Marsha Lanza told the newspaper. “I didn’t know that they [the guns] would be used on her.”

Members of Nancy Lanza’s regular neighborhood dice game never got inside her home, either — not in 15 years of regular games. Rhonda Collens, a frequent player in the game, said that while the group’s weekly get-togethers moved from house to house, Nancy Lanza’s was always skipped. She never met Adam Lanza, and Nancy never spoke of her children. Adam has an older brother, Ryan Lanza, who lives in New Jersey and works for the accounting firm Ernst & Young.

Asked about Nancy Lanza’s guns, Collens said, “I had no idea she liked that stuff,” adding, “she was a nice lady, very pleasant.”

Adam Lanza’s acquaintances continued coming forward with what they knew about a young man who to many seemed unknowable. They described him as a loner, shy, brilliant, interested in gaming and computers, though seemingly without a digital footprint on social networks. It was not known whether he had a job.

Kate Leen, 21, attended seventh and eighth grade with Lanza and remembers him as very shy.

“You would say ‘hi,’ and he would say ‘hi’ back, but he didn’t give you a lot to work with,” said Leen, who now attends Hofstra University in New York.

In high school he dressed in khaki shorts and pants and wore oversize button-down shirts. He carried a briefcase instead of a backpack.

“He wasn’t exactly extra welcoming,” Leen said.

Marsha Moskowitz, his middle-school bus driver, didn’t remember Adam Lanza having any friends on the bus. “He was very, very quiet, reserved, shy, kept to himself,” she said. “He’d say hello and goodbye, and that was about it.”

Although private, the family wasn’t isolated.

Acquaintances recall that Nancy Lanza was a regular presence at My Place, the town watering hole and eatery. She liked craft beers, Holmes said.

“I guess now we’ll all be looking a little bit closer at things,” Holmes said, “though she seemed a normal, everyday lady.”

Rosenwald reported from Washington. Eli Saslow, Jennifer Jenkins and Alice Crites contributed to this report.