Source: Adam Lanza had cut off ties with his father

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By Jeff Rossen and Robert Powell

We've heard a lot about Adam Lanza and his mother, but now we have new information about his relationship with his father, Peter. A source close to the family told NBC News that Adam had cut off communication with his father, refusing to see him.

In the chaotic hours after Adam Lanza's rampage, a local reporter showed up at his father's doorstep to break the news. "His expression twisted from patient, to surprise, to horror," said Maggie Hogan of the Stamford Advocate. "It was the first time that he considered a loved one could be involved."

Peter Lanza is a successful finance executive at GE, part owner of NBC Universal. A source close to the family said that in 2001, he separated from Adam's mother, Nancy, but he still saw Adam every week. In 2009, the Lanzas officially divorced, when Adam was 17.

Martha Lanza, Adam's aunt, said: "They were the type of parents, even when they were married, even as well as being separated, if the kids had the need, they would definitely fill it."

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But the source close to the Lanza family said that by 2010, Peter Lanza was dating a new woman, whom he later married, and Adam suddenly cut his dad off, despite his father's attempts to see him. Peter Lanza hadn't seen or heard from his son since then.

Now NBC News has obtained the divorce documents between Adam's parents. Peter and Nancy agreed on joint legal custody of Adam. He lived full-time with his mom, in a spacious Connecticut home. And Adam's dad was fully supporting them, with hefty monthly payments: this year, more than $289,000 in alimony. Peter also volunteered to pay for Adam's college, car and medical insurance.

"This was a very friendly divorce," said Connecticut divorce attorney Eric Broder. "The parties represented themselves, and they seemed to reach an agreement that they both found fair and equitable. I would take 10 clients like this any day, nice and easy."

According to their divorce mediator, Adam's parents were concerned about his needs, and Nancy didn't like to leave him alone. The source close to the family told NBC News that Adam's father never saw any violent behavior from him.

"When the parents divorce, those children feel lost," said Jeff Gardere, psychologist and NBC News contributor. "There is an impact on every child who is part of that divorce. They can feel guilty. The foundation that they've had in their lives, the stability is now being torn asunder."

Right now, no one knows what caused Adam's violent spiral. His father hasn't spoken publicly, just releasing a statement saying that he can't comprehend what has unfolded; he's saddened and struggling to make sense of it, and he's cooperating fully with law enforcement.