Eric Harris' parents are in hiding. But students who knew the suspected killer believe his parents never suspected there was a monster in the house.
"Eric is an evil genius, I guess," said Brooks Brown, who was friends with Harris. "Really conniving, but brilliant."
Dylan Klebold's parents now tell friends they never knew the dark side of their son, reports CBS News Correspondent Bob McNamara.
"They are devastated. Devastated," Judy Brown, a Klebold family friend, said. "And they think the world will hate them, and they didn't have a clue. I know these people. They didn't have a clue."
But 17-year-old Dylan Klebold and 18-year-old Eric Harris left clues everywhere.
At Black Jack Pizza, Harris ranted at work about "the things that bothered him, the same things that really made him mad. It's the same things he wrote on the Internet," remembered Michelle Hartsough, a former coworker.
On the Internet, Harris was all hate and hit lists.
"There were information on how to make pipe bombs, and that they had been exploding pipe bombs," said Brown.
A year-and-a-half ago, Randy and Judy Brown twice alerted Jefferson County police to Harris' violent web page.
"The police department was handed this on a silver platter and did nothing," contends Mrs. Brown. "Amen, that's how I feel. They had the information. It's their job."
While it may have been the Dylan Klebold and the Eric Harris from childhood photos that their parents saw, the Harris and Klebold most students and teachers knew were outcasts, members of the Trench Coat Mafia.
They were kids whose fascination with violent video games was the model for their own video class project, in which they stormed the Columbine High School halls and cafeteria killing students.
But nobody told school officials.
"The first time I heard that term 'trench coat mafia' was after this happened," said Frank Deangelis, Columbine's principal.
"Professionals can always be fooled," said clinical social worker Teri Pichot, who has counseled Columbine students. "There is a culture in any adolescent group of 'don't narc', be treated how you want to be treated. There's an us-against-them mentality that is crucial to growing up."
After school shootings elsewhere last year, federal education experts issued a school guide to spotting warning signs of trouble -- including possession of weapons, prejudicial attitudes and threats of lethal violence.
Harris and Klebold matched all those signs and more, but few spoke up, and guilt has set in.
"I could have done this and I could have done that," said Hartsough. "A lot of things I could have done but I didn't."
Pichot has counseled at three separate school shootings. Does she think there will be more?
"Unfortunately, probably so," she said. And probably the warning signs are there.