CRYSTAL LAKE (CBS) — Before 20 year-old Adam Lanza headed to the school he killed his mother, Nancy, in her home.

CBS 2’s Courtney Gousman spoke with Nancy’s former sister-in-law Saturday morning in Crystal Lake, and learned a lot more about the killer.

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Police say Nancy Lanza was shot and killed in her home by her son, who would go on to gun down 20 children and six adults at this elementary school.

“Oh it shocked us all right to the core. Like I said to my husband did you ever think? He said no, this just blows me away,” said Marsha Lanza, Adam Lanza’s Aunt.

Marsha is still troubled. She lives in Crystal Lake, a far cry from the horrific scene at Sandy Hook Elementary.

It’s also the school Marsha Lanza believes her nephew Adam started his academic career. He would later be pulled out by his mother.

“I know she had issue with school. She eventually wound up homeschooling him. She battled the school district. If it was behavior, if it was learning disabilities, I really don’t know, but he was a very, very bright boy. He was smart,” said Marsha.

Lanza says she believes her nephew was recently taking college courses, and had a keen interest in computers.

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Marsha frequently corresponded with Nancy Lanza, through Facebook and email knew her sister-in-law, a single-parent, owned three guns.

“For self-defense and no other reason, because they were not a violent family,” said Marsha.

Marsha says her sister-in-law never spoke of any serious issues with Adam, and now this aunt is left asking some of the same questions many others are echoing.

“Why these kids? Why these innocent little kids? That just still baffles me.”

Marsha Lanza says Adam’s parents have been divorced since 2008.

The last time she saw her nephew, he was three years-old.

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Marsha says the concern now, is for her brother-in-law, Adam Lanza’s father. They haven’t been able to reach him since the shooting.