But, CBS News Correspondent Cynthia Bowers reports, Pastor Don Marxhausen, the minister for the Klebold family, says Dylan's parents were not negligent.
"I had the same initial reaction when I heard what happened," he tells Bowers. "I said, 'Boy, some parents really screwed up here'Â… When I found out it was [the Klebolds], my first response was, 'Something's wrong here,' because I know them to be very loving, caring parents, and their children are probably the foremost thing in their minds."
Marxhausen presided over Dylan's funeral over the weekend. He tells Bowers, "I think [the parents] are partially in shock at the moment. I think they're partially held together by some friends who came and supported them at the funeral. I think they're more into disbelief. Between tears and disbelief. Going back and forth."
What kind of boy was he?
"They loved him," says Marxhausen. "And they thought he was, as the father said, just about a finished product, ready to go off to college next year."
In hindsight, after the tragedy, the Klebolds are wondering if there were signs that they missed.
"The father, who thought he had a soul mate in his son, the Friday before felt Â… stress in his son," says the pastor. "He made a mental note and said, 'I have to get back to my son on this.' And then the mother said, the day of the shooting, she felt a fatalistic tone, and didn't know where this came from, when he said goodbye. And that's all they could remember."
And, perhaps the most difficult question of all, are Dylan Klebold's parents feeling responsible for the tragedy?
"Not yet," says their pastor. "They know on an intellectual level their son did this. But they can't yet own it inside themselves."
At Sunday's memorial, Bowers asked some mourners if they thought the parents were partly to blame. Here are some of the responses:
"Where have they been the last, who knows, several years, probably?"
"I'm open-minded. My heart is open to them. As a parent, my kids are young. But I wonder how you could go through something like that and there be absolutely no warning signs that there are problems."
Many feel there probably were signs that Klebold's and Harris' families did miss:
"I think there is responsibility that needs to be taken by the parents. I guess I would expect the same from the community, if I were the parent, that I should shoulder some of the blame also."
"They're parents. I'm sure they're grieving. But, at the same time, I can't help but feel that they should be a little accountable for this."
If there is a lesson to be learned from this tragedy, parents in Littleton say it is that we all need to pay more attention to children.
"You ave to know what your kids are doing. You have to know what they're watching, and take an interest in them, whether they like it or not, because at times like this, they know it was love."