The FBI on Wednesday said a woman who is “infatuated” with the mass shooting at Columbine High School — which occurred April 20, 1999 — should be considered armed and “extremely dangerous.”

Denver-area public schools are closed today as authorities search for Sol Pais, 18, who flew to the city from Miami and bought a pump-action shotgun and ammunition. The FBI says she “made threats to commit an act of violence in the Denver metropolitan area.”

“All schools in the Denver area were urged to tighten security because the threat was deemed ‘credible and general,’ said Patricia Billinger, a spokeswoman for the Colorado Department of Public Safety,” the Associated Press reported. “Columbine and more than 20 other schools outside Denver lock their doors for nearly three hours Tuesday afternoon before Wednesday’s complete closures were announced.”

The @FBIDenver & JCSO are asking for the public’s help regarding a potential credible threat. Last night Sol Pais traveled to Colorado & made threats. She is armed & considered to be extremely dangerous 1/3 pic.twitter.com/2x5iwddsMp — Jeffco Sheriff (@jeffcosheriffco) April 16, 2019

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Saturday marks the 20th anniversary of the mass shooting at Columbine. Twelfth graders Eric Harris and Dylan Klebold murdered 12 students and a teacher before committing suicide.

“This has become a massive manhunt,” Dean Phillips, head of the Denver office of the FBI, which is leading the investigation, said, according to the Washington Post. Pais was “last seen in the county’s foothills, clad in camouflage pants, black boots and a black T-shirt,” the Post reported.

FBI agents were seen entering Pais’s home in South Florida Tuesday night. A man who identified himself as her father told the Miami Herald of his daughter: “I think maybe she’s got a mental problem.” Pais’s parents reported the teenager missing Monday night, after losing contact with her on Sunday. “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 said, “we consider her to be a credible threat — certainly to the community and, potentially, to schools.” The threat, which the FBI said was “not isolated to one school or individual,” led county public school officials on Tuesday afternoon to place Columbine and nearby schools on “lockout,” which means classes continue as usual inside while entries to and exits from the building are restricted.

“We’re looking for her everywhere,” Mike Taplin, spokesman for the Jefferson County Sheriff’s Office, said Wednesday morning, the Denver Post reported. “We’re hoping to find her before any bad can be done. All the jurisdictions are working together and the FBI is the lead agency.”

He added: “If someone sees her, they need to call 911 immediately and not try to contact her because she is considered armed and dangerous.