"She died on Friday morning at 5.05am, and the shooting happened at 9.30am," Dearth told the Herald on Sunday.
The Sandy Hook tragedy felt particularly close, especially when he and his family discovered their mother's body lay in the same funeral home as some of the 20 children killed.
They found that out from the funeral director, who impressed them with his professionalism and calm manner. "He was like a rock," said Dearth.
Dearth's brother Bob, thinking aloud, had said: "I suppose some of the kids are here?"
The funeral director replied: "Yes, as a matter of fact we just had six come from the hospital. We went and picked them up."
"I saw a crack in his armour for a moment," said Dearth. "There was a quiver and shakiness in his voice. He was deeply affected by it."
Dearth and wife Annette moved to New Zealand about 11 years ago and are proud parents of two little Kiwi kids, Ezra Phoenix, 5, and Lucia Rose, 3.
Dearth said he and Annette lived here because they loved New Zealand, not because they had fled the United States.
Yet he felt a rekindled "fire of happiness" and appreciation of his life here.
The killings at Sandy Hook have sparked debate on US gun-control laws.
"I don't have a problem with someone wanting to own a gun," he said. "But you don't have to own a machine gun. It's getting a bit stupid. I think now it's finally going to change."
It was sad and unfortunate that his mother died, "but she had lived a life. She was here for 66 years. Not like these families affected at this time of year, it's horrible. You can't comprehend the pain they're going through."
Meanwhile, Peter Andrew, a former New Zealander who now lives in Newtown, said his family was "hanging in there".
Last week he spoke of how he and wife Andrea had told their 8-year-old son Gregory of the mass shooting.
He said Newtown now wanted the hordes of media to leave so the town could grieve and heal.
