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(CNN) - After every shooting like the one at Arapahoe High School in Colorado Friday, the same two questions are asked: Why? And could this have been prevented?
Often people seek answers from the parents of the killer, who are quite often not forthcoming. Some parents go into hiding.
"It's very comforting to hold the parents of the killers accountable, it makes us feel like the situation can be controlled," said Andrew Solomon, author of "Far From the Tree: Parents, Children and the Search for Identity." Solomon interviewed the parents of Colombine shooter Dylan Klebold multiple times over seven years.
But blaming parents is often misguided, says Solomon.
"Some of these kids come from very disturbed homes, but many of them have extremely loving parents who are trying to pay close attention to them," said Solomon. The Klebolds "were really quite wonderful parents, and they had no idea what was going on in their son's head."
Mother Sue Klebold understood her son's struggles only after the Colombine shooting.
"What I've learned from being an outcast since the tragedy has given me insight into what it must have felt like for my son to be marginalized. He created a version of his reality for us: to be pariahs, unpopular, with no means to defend ourselves against those who hate us," Sue Klebold told Solomon for his book.
The Klebolds said they were worried Dylan was struggling, but it was nothing major, "and certainly nothing threatening to other people," said Solomon.
"After it took place, they were in a state of complete shock. It was inconceivable to them that the child they knew would be capable of such a thing," said Solomon.
The mother of the Sandy Hook shooter, Nancy Lanza, was one of her son's victims. But she was also the one who connected Adam Lanza with guns and watched his emotional disintegration into a pit of violence and anger.
"It's clear that if she thought that he was dangerous, she would not have left the guns sitting out, since he used one of them to kill her," said Solomon.
"She was bewildered by her own child," said Solomon.
The Lanzas did in fact seek help, visiting a number of psychiatrists for Adam to help him function with Asperger's syndrome.
"None of the professionals who saw him ever picked up on the possibility that he could pose an acute danger to anyone else, or to himself," said Solomon.
"We all like to think we know our children, that we know their inner lives. But people keep secrets from their parents," sad Solomon.
CNN's Jessica Metzger contributed to this report.