Charles Manson. Adolf Hitler. Violent artwork. Pipe bombs.
On Thursday, authorities released nearly 1,000 pages of hate-spewing diary entries and homework that provided chilling new insights into the Columbine massacre.
It was April 20, 1999, that Dylan Klebold and Eric Harris went on a deadly shooting rampage at Columbine High School in Littleton. Colo., that left 15 dead, including themselves.
"In retrospect, we're like, 'Yeah, why didn't somebody do something?'" said Steve Saunders, a reporter for KMGH-TV in Denver who has covered the story since the attack. "But at the time it was just, like, inconceivable that that would happen."
The release of the documents has caused fresh pain for Columbine parents and more proof, some say, that the bloodshed might have been prevented.
"The school knew about the pipe bombs," said Brian Rohrbaugh, whose son, Daniel, was killed in the shootings. "The police knew about the pipe bombs. The families knew about the pipe bombs. So there's just a mountain of information that shows it should never have happened."
The parents of both killers have long chosen not to give interviews, but a journal written by Eric Harris' father, which was among the documents released Thursday, sheds light on what appears to be talks with therapists, police and lawyers about his son.
"This was a father who was attempting - if not successfully, but certainly attempting - to get his son help," said Harold Koplewicz, director of the New York University Child Study Center in New York.
The documents reveal months' worth of angry notes with talk of "killing mankind," a receipt from a gun store, and a calendar "to-do list" that includes notes to "get nails," "get propane," and "fill my clips."
There is an essay that Harris wrote about school shootings years before committing the killings at Columbine.
The documents show that the boys had "long-term problems," Koplewicz said.