Lanza died this past week when her 20-year-old son Adam shot her several times in the head before going off to the school where he shot and killed 20 children and six adults before taking his own life.
An unidentified friend of Nancy Lanza said she had confided while they shared a drink less than a week before the massacre that Adam, who he never met, was struggling and "getting worse," the New York Daily News reported Sunday.
"She just looked down at the glass and said, 'I don't know. I'm worried I'm losing him,'" the friend said. "She said it was getting worse. She was having trouble reaching him.
"I asked her if she was getting him help and she said she was," he added.
The friend said Adam had inflicted injuries on himself in the past.
"Nancy told me he was burning himself with a lighter. In the ankles or arms or something," he recalled of a conversation a year earlier. "It was like he was trying to feel something."
The friend said Lanza talked more about her other son Ryan.
The friend described Nancy as "a country girl" who used a falcon to flush prey she would shoot. Lanza owned "at least a dozen" guns, mainly rifles.
"Adam learned how to shoot a rifle by the time he was 9 years old," the friend said. "They would go to the range.
"Nancy was a responsible gun owner. It was important that she teach her son how to responsibly use a firearm."
She "didn't get along" with her ex-husband, Peter Lanza.
"I don't think she ever saw him," the friend said.
The Washington Post reported Nancy's landscaper, Dan Holmes, said guns were her "hobby."
"She told me she liked the single-mindedness of shooting," he said.
Holmes said she even spoke of taking her son to the firing range to practice his aim.
Holmes said he never went inside Nancy's home and never saw Adam.
"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."
Marsha Lanza of Crystal Lake, Ill., Nancy's former sister-in-law, told the Chicago Sun-Times Nancy wanted guns for protection. "She prepared for the worst," Marsha Lanza said. "I didn't know that they [the guns] would be used on her."
The New York Times reported Nancy, who was divorced in 2008, was described by friends as social and generous to strangers, but also high-strung. She struggled to help Adam cope with a developmental disorder that often left him reserved and withdrawn, relatives, friends and former classmates told the Times. She home-schooled him for a time.
Peter Lanza, an executive at General Electric, said in a statement Saturday night that he was cooperating with authorities. "We are in a state of disbelief and trying to find whatever answers we can," he said. "We, too, are asking why.
"Like so many of you, we are saddened but struggling to make sense of what has transpired."
Nancy's brother, former police officer James Champion of Kingston, N.H., declined to discuss Adam's mental condition Saturday, noting he had not seen him in eight years, the Times said. He said her sister had not been working, but had once been a stockbroker.
"On behalf of Nancy's mother and siblings, we reach out to the community of Newtown to express our heartfelt sorrow for the incomprehensible loss of innocence that has affected so many," Champion said in a statement.