DENVER The F.B.I. said a Florida high school student was no longer a threat on Wednesday after she made threats that prompted hundreds of schools to close across the Denver area.
Identified as Sol Pais, 18, the woman had traveled to Denver and bought a firearm ahead of the 20th anniversary of the Columbine High School shooting, officials said.
The authorities said Ms. Pais was considered armed and extremely dangerous, and the decision to keep about half a million students home in two dozen school districts showed the sense of alarm among officials.
An F.B.I. bulletin sent to local law enforcement agencies on Tuesday said Ms. Pais was infatuated with the Columbine attack, and officials expressed concerns about her mental stability. She had also purchased a shotgun and ammunition after arriving in Denver, the authorities said.
Ms. Pais, a student at Miami Beach Senior High School, had last been seen wearing a black T-shirt, camouflage pants and black boots, the authorities said.
In a news conference Tuesday night, Dean Phillips, the special agent in charge of the F.B.I.s office in Denver, said the search had turned into a massive manhunt. Mr. Phillips said his team had received a tip Tuesday morning from federal agents in Miami identifying Ms. Pais as a possible threat in Colorado.
School superintendents throughout the Denver area decided during a conference call on Tuesday night to jointly close schools on Wednesday morning as a precaution, The Denver Post reported.
Ms. Paiss parents reported her missing to local police on Monday, Detective Sergeant Marian Cruz, a spokeswoman for the Surfside Police Department, said on Wednesday. Police have not been called to the familys address before, she added.
Daisy Gonzalez-Diego, a spokeswoman for the Miami-Dade County Public Schools, confirmed on Wednesday that Ms. Pais is a student at Miami Beach Senior High School. The school district is assisting the F.B.I. with its investigation, Ms. Gonzalez-Diego said.
In a news conference Tuesday night, Dean Phillips, the special agent in charge of the F.B.I.s office in Denver, said the search had turned into a massive manhunt. Mr. Phillips said his team had received a tip that morning from federal agents in Miami identifying Ms. Pais as a possible threat in Colorado.
The F.B.I. then discovered that Ms. Pais had arrived at the Denver airport and bought a pump-action shotgun and ammunition at a store. She was then taken to an area where she was last seen out toward the foothills, Mr. Phillips said.
Because of her comments and her actions, because of her travel here to the state, because of her procurement of a weapon immediately upon arriving here, he added. We consider her to be a credible threat certainly to the community and, potentially, to schools, he said.
The search for Ms. Pais quickly upended families across the Denver region. Thousands of parents woke on Wednesday morning to discover that schools had been canceled and that they would have to explain the cancellation to their children.
For some of the youngest students, this was their first introduction to the Columbine shooting, and to its legacy.
Some parents decided that they would keep their children inside all day; others said this would effectively hand Ms. Pais a victory.
Its sad and scary, said Jeff Desserich, a math teacher at a charter school in Denver, who spent the morning trying to explain to his daughters Anais, 8, and Elena, 6, why they would not be going to class.
I said, There is a lady, she probably has some sort of mental health issue, he said, And I talked a little about the sad events of Columbine and how her flying to Denver and buying a weapon, thats a really big flag for law enforcement.
She would definitely be avoiding a popular new playground in the area.Because Im worried, she said, Im concerned that if she is intent on carrying out a plan that she has in mind, that if schools are no longer on option, that shell move farther into the mountain districts, or down to Colorado Springs, or shell stay in Denver and carry her plan out in a place saturated by children.
Just last Friday, Colorados Democratic governor signed a red flag law that would allow guns to be temporarily seized from people deemed to be dangerous to themselves or others. The act was bitterly opposed by more than a dozen sheriffs and officials from largely rural, conservative counties who vowed not to enforce it.
The state also passed significant gun control measures in 2013 that expanded background checks, but despite that, Colorado does not have a specific waiting period for someone who wants to buy a gun.
In Florida, The Miami Herald reported that a man who answered the door at Ms. Paiss address on Tuesday identified himself as her father and said he had lost contact with her on Sunday. I think maybe shes got a mental problem, he told The Herald. I think shes 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 shootings 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.
Jefferson County, home to Columbine High School, has spent the past 20 years grappling with that legacy.
Students, teachers, families and law enforcement officers have had to deal not only with the emotional trauma of the shooting, but also with the people who have become obsessed with it and the copycats who have carried out their own attacks.
In an interview last year, the head of safety for Jefferson County schools, John McDonald, said he had often apprehended people who came from around the country to try to enter the school, a major safety concern. These visits and interest in the shooting have only increased over time, he said: Ive been dealing with this for more than a decade, and its never been more of an issue than it is now, 20 years later.
Anemona Hartocollis contributed reporting from New York and Patricia Mazzei from Miami.