Parents who have coped with an unimaginable loss of this kind often have to live with the realization that they tried to do the right thing, but it turned out all wrong.
That's certainly the case for the father of Brad Hoffman Parker, who says he restricted his then-12-year-old son's computer access after he ran up an exorbitant Internet bill, often secretly in late-night chatrooms.
On a September night in rural Missouri some 12 years ago, Brad shot his mother six times in the head before turning the gun on himself.
"I look back at so many things I said and did that I wish I could take back," his father, David Lee Parker, told ABCNews.com.
Brad was a gifted student whose grades slipped when he was moved to a rural town where he didn't quite fit in, and took solace in his computer.
His father said he and his ex-wife, Ann Hoffman, had seen Brad's psychologist the morning of the murder-suicide. While he agreed with the discipline, Parker said the psychologist countered that the complete computer restriction might have been too harsh for the circumstances.
"I don't know how many times I've gone over that in my mind," Parker said. "I stuck to my guns and I wish I hadn't."
Parker said he never would have dreamed his son would be capable of such a crime and knows in his mind that he did everything he could for his son. But his heart tells him something different.
"Being a parent was really the only job I had and I blew it," he said.
ABC News Research's Melissa Lenderman contributed to this story.