A manhunt is underway for an “armed and extremely dangerous” woman, whose obsession with the Columbine school shooting forced all schools in the Denver area into lockdown on the massacre’s 20th anniversary Tuesday. The woman, 18-year-old Sol Pais, flew from Miami to Colorado Monday night and immediately went to a store and bought a pump-action shotgun and ammunition, said FBI Special Agent in Charge Dean Phillips at a news conference Tuesday night. “She has made concerning comments in the past,” Phillips said. “She has expressed an infatuation with Columbine.” Police said that many schools in the area remained closed on Wednesday and others ramped up security, as they continued their search for Pais, who was last seen in the foothills of Denver wearing a black T-shirt, camouflage pants, and black boots, according to the FBI. “We have been trying to find her ever since,” Phillips said. “We consider her to be a credible threat, to the community, and certainly to schools.” The Jefferson County sheriff’s office said Pais made “threats to commit an act of violence in the Denver metropolitan area.” Authorities said that no specific school was considered to be vulnerable, and it’s not clear when or how she communicated those threats. Phillips said that the FBI was working with the U.S. Attorney’s office to figure out what they could charge Pais with, if she's arrested. In April 1999, two gunmen, aged 17 and 18, shot and killed 13 people in the massacre at Columbine High School before turning the guns on themselves. The infamy of what’s often considered the first school shooting of the modern era has produced a bizarre online community, consisting of Columbine-obsessed bloggers — including many teenage girls — who worship school shooters like heartthrobs. Pais’ family is urging that she return to Florida. “She can, please, come home,” her father, speaking through a closed door, told CBS Miami . "It's like a bad dream.” Her father added that he thinks “maybe she has a mental problem.” Cover image: Mugshot of Sol Pais, courtesy of FBI.