Dylan Klebold's school compositions, which included descriptions of a killing, were brought to the attention of his mother, Susan Klebold, and of his school guidance counselor, said Marilyn Saltzman, a spokeswoman for the Jefferson County Public Schools. Klebold, a senior, dismissed the writing as "just a story" in conversations with his counselor, whom Ms. Saltzman declined to identify.
An essay in which Eric Harris portrayed himself as a shotgun shell prompted the same teacher to have a similar talk with his father, Wayne Harris. Once the teacher learned that Harris was a retired Air Force officer and that his son hoped to enlist in the military, she concluded that the essay was consistent with his future career aspirations, Ms. Saltzman said.
A classmate, Kevin Hofstra, recalled recently that Eric Harris had written about "some strange stuff."
"One assignment was to write about an inanimate object," Hofstra said. "Most people would choose a bicycle or something. He chooses a shotgun shell and writes about his relationship with the barrel. He often wrote about shotguns."
A video produced at the school and broadcast last week by the syndicated program "Inside Edition," also had elements of foreboding.
The video, produced two years ago in film class and intended to be humorous, shows students wearing black trench coats and carrying guns as they move through the school's hallways. As four students walk away from Columbine, the school explodes in orange flashes.
Eric Harris and Dylan Klebold did not appear in the video, which was partly edited by Brooks Brown, a classmate who knew the pair well. In a coincidence, another editor of the video, a 1997 Columbine graduate, is the son of Dwayne Fuselier, the lead F.B.I. investigator in the killings at the school on April 20. An F.B.I. spokesman has said the agency has full confidence in Fuselier, a 51-year-old psychologist.
School officials have declined to allow interviews with the teen-agers' English teacher or with their film teacher.
In the wake of the shootings, the family of Isaiah Shoels, the only black victim in the killings at the high school in Littleton, Colo., has hired Geoffrey Fieger, the Michigan lawyer who won the Jenny Jones talk show case last Friday. Fieger has said he may sue Jefferson County Public Schools for negligence. Michael Shoels, Isaiah's father, has accused a Columbine dean of ignoring a complaint he made in early April that his son had received racist death threats from the trench coat mafia, a school clique that included Eric Harris and Dylan Klebold.
Almost three weeks since the killings in Littleton, about 80 investigators are working on the case, evaluating about 10,000 pieces of evidence, 1,800 tips and 1,300 interviews.
In the only arrest so far, Mark E. Manes, a 22-year-old neighbor of the gunmen, was charged on Monday with providing a minor with the handgun used in the attack. Manes, the police say, supplied one boy with a Tec-DC9 assault pistol on Jan. 23.
Searching for clues and possible confederates of the two gunmen, investigators have also submitted a friend of the pair to a lie detector test and have scoured the park areas of Eric Harris's neighborhood for the remains of old pipe bombs.
Brooks Brown, a neighbor of the Harrises, has said that the pair used to set off bombs in the neighborhood. Employees at a Blackjack Pizza delivery outlet, where the young gunmen used to work, have said that on one occasion in the past year Eric Harris displayed a pipe bomb to co-workers at the store. He was on juvenile probation at the time.
New evidence has emerged that in the minutes before their attack on Columbine, the gunmen used timers to set off two diversionary bombs, one four miles away, the other two miles away. The goal apparently was to confuse and delay police and fire workers responding to emergency calls from the high school.
Each bomb, hidden in a backpack, was based on two 16-ounce camp-stove-size propane tanks. Passers-by have said one bomb sent up two successive fireballs, each 40 feet high and 7 feet in diameter. The gunmen had less luck with a 25-pound propane bomb in the school kitchen.
Judging by a pattern of bullet holes in the kitchen wall and from a security videotape recovered from the cafeteria, investigators believe that, when this bomb failed to detonate, the frustrated attackers repeatedly shot at the propane tank.
Still shocked by the attack, Columbine students and their families received several morale boosters in recent days.
On Saturday night, in an event closed to the press and billed Columbine Surprise Party, players from two of Denver's professional teams, the Super Bowl champion Denver Broncos and the Colorado Rockies baseball team, mingled with 1,500 Columbine students and family members at a nearby high school, signing autographs and eating pizza.
On Sunday, Shania Twain, a country singer who was in Denver for a concert, visited the five Columbine students who remained hospitalized.
On May 20, one month after the killings, President Clinton is scheduled to visit.
On Monday, dozens of volunteers started dismantling a shrine covering the size of a football field in a park adjoining Columbine High School. On Sunday, for the second time, votive candles sparked a fire, which consumed a canopy tent, bouquets, scraps of poetry and stuffed bears.