Newtown parents describe meeting with killer's dad

Instead, the Parkers said they and Peter Lanza shared their condolences for one another and talked about his son, Adam Lanza, during the emotional meeting, which lasted more than an hour.

"I don't feel like he should be held responsible for what happened that day," Alissa Parker told "CBS This Morning" during the second part of an interview that aired Friday. "That was not ultimately his decision to do that, so how can I hold him responsible? Were there missteps in the raising of his son? Possibly."

Adam Lanza, 20, fatally shot 20 children and six educators with a military-style rifle on Dec. 14, then killed himself as police arrived. Authorities say he also killed his mother, Nancy, at their Newtown home before he went to the school. The Parkers lost their 6-year-old daughter, Emilie, in the rampage.

Alissa Parker said she told Peter Lanza that there was an opportunity to learn from the killings and his cooperation was vital.

The Parkers wouldn't reveal what Peter Lanza said about his son. Connecticut state police haven't released any information about a motive, but people close to the investigation have told The Associated Press that Adam Lanza showed interest in other mass killings and had literature on other mass shootings at his home. The people spoke on condition of anonymity because the investigation is continuing.

Peter Lanza, who was divorced from Nancy Lanza, has declined to comment about the meeting with the Parkers, who said they came away from it with a better understanding of Adam Lanza.