DENVER Hundreds of schools across the Denver area were closed on Wednesday as law enforcement officials search for a Florida woman who they said had made threats ahead of the 20th anniversary of the Columbine High School shooting and was considered armed and extremely dangerous.
The decision to keep about half a million students home in two dozen school districts over a vast swath of Colorado showed the sense of alarm among the authorities. An F.B.I. bulletin sent to local law enforcement agencies on Tuesday identified the woman as Sol Pais, 18. She was infatuated with the Columbine attack, the bulletin said, and had been attempting to buy firearms.
School superintendents from 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. Pais is about 5-foot-5 with brown hair and was last seen wearing a black T-shirt, camouflage pants and black boots, authorities said. She had recently traveled to Colorado, law enforcement officials said. An F.B.I. official expressed concerns about her mental stability.
Ms. Pais parents reported her missing to local police on Monday, Detective Sergeant Marian Cruz, a spokeswoman for the Surfside Police Department, said on Wednesday. That has been the only time police have been called to the familys address, 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 before buying 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.
Her comments, her actions that we have heard about from others tend to cause us great concern that she may pose a threat to a school, he added.
If authorities find Ms. Pais, it is not clear if they can arrest her. The bulletin sent to local police said they did not have probable cause for arrest, but that officers should detain her and evaluate mental health status.
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. 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 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 the event became a source of inspiration for future attackers. 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 people who have become obsessed with it, as well as 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.
The approaching anniversary has put many people in the region on edge, and in the last week, the county has implemented lockouts on multiple days.
Julie Turkewitz reported from Denver and Anemona Hartocollis reported from New York. Jack Healy contributed reporting from Denver and Patricia Mazzei from Miami.