Hundreds of Denver Schools Are Closed as F.B.I. Seeks Woman ‘Infatuated’ With Columbine

In Florida, The Miami Herald reported that a man who answered the door at Ms. Pais’s address on Tuesday identified himself as her father and said he had lost contact with her on Sunday. “I think maybe she’s got a mental problem,” he told The Herald. “I think she’s going to be O.K.”

In Colorado, the announcement prompted “lockouts,” or heightened security measures, at schools in Jefferson County and the surrounding area on Tuesday. During a lockout, all exterior doors are locked at a school but business continues as usual inside. Police officers aided in end-of-day student release. County officials said that all students and staff members were safe.

It was not the first threat for students at Columbine High School. In December, an anonymous caller claimed bombs had been planted inside the school. Police responded, but the threat proved to be a hoax.

During the Columbine High School shooting on April 20, 1999, two students shot and killed 12 of their classmates and a teacher.

The shooting’s aftermath was widely televised, and young people across America continue to be influenced by the symbology of the Columbine shooting and the students who carried it out, according to law enforcement officials, researchers and educators.

In May 2018, a 17-year-old junior in Santa Fe shot his teachers and fellow students with a sawed-off shotgun while wearing a black trench coat and carrying Molotov cocktails, his arsenal and attire inspired by the Columbine gunmen. The 20-year-old attacker who killed 26 people at Sandy Hook Elementary School in Connecticut in 2012 had compiled materials on the Columbine attackers on his computer. And in his manifesto, the 23-year-old student who shot and killed 32 people at Virginia Tech in 2007 had called the Columbine gunmen by their first names and described them as “we martyrs.”

The killers have achieved dark folk hero status in the corners of the internet where their carefully planned massacre is remembered, studied and in some cases even celebrated, officials say. Their admirers, often known as “Columbiners,” are frequently depressed, alienated or mentally disturbed, drawn to the Columbine subculture because they see it as a way to lash out at the world and to get the attention of a society that they believe bullies, ignores or misunderstands them.