UPDATE: Nearly half a million schools on Colorado’s Front Range closed Wednesday due to the manhunt for Sol Pais.

JEFFERSON COUNTY, Colo. (CBS4)– Columbine High School and several other schools in the Jeffco Public Schools district were placed on lockout Tuesday afternoon due to “a credible threat.” The FBI is searching for Sol Pais, who is considered armed and extrememly dangerous.

“This has become a massive manhunt,” investigators said in a news conference at 9:30 p.m. Tuesday. Investigators say Pais is “infatuated with the perpetrators of Columbine” and traveled from Florida to Colorado. She obtained a pump action shotgun in Colorado, investigators said.

Sol Pais (credit: Jefferson County)

The FBI is investigating the threat that initially was based in Jefferson County but actually includes schools in the Denver metro area. Anyone with information is asked to call the FBI Tipline at 303-630-6227.

20 YEARS LATER: Columbine Legacy

Pais is 18 years old and described as a white female, 5-foot-5, with brown hair and was last seen wearing a black T-shirt, camo pants and black combat boots. She was last seen in the foothills of Jefferson County after she traveled to Colorado on Monday night and made threats in the Denver metro area.

“Last night Sol Pais traveled here to Colorado and she made threats to commit an act of violence in this area, she is armed and considered dangerous,” said Mike Taplin with the Jefferson County Sheriff’s Office.

Anyone who sees Pais is asked to stay away from her and call 911 immediately.

The suspect’s family is asking her to turn herself in. Our CBS station in Miami talked with her father through a closed door at the family home in Surfside.

“It’s like a bad dream. We don’t know. We don’t have any ideas,” he said. “I think that maybe she has a mental problem.”

Schools across the Denver metro area were included in the threat, including Jeffco Public Schools, Cherry Creek Schools, Denver Public Schools, Clear Creek Schools, and Westminster.

Jeffco Public Schools said that in addition to Columbine and Leawood Elementary, all mountain schools were also placed on lockout. That means that it is business as usual inside the buildings but the entries and exits are restricted.

All after school activities, sports and practices will happen as scheduled except for Columbine, according to Jeffco Public Schools. Students will be released at their normal time but will remain under lockout until then.

Denver Public Schools said that all their schools will have after school activities on Tuesday but the activities were moved inside.

Saturday marks 20 years since gunmen killed 12 students and one teacher at Columbine High School.

Aurora Public Schools canceled all after school activities for Tuesday.

Aurora police tweeted that they are also also investigating the threat, which they said is “to schools in general.” The Aurora School District says they are increasing police presence at their schools.

Kent Denver canceled its after school activities.

Schools impacted by the threats canceled classes on Wednesday.

LINK: Talking to Children About Violence: Tips for Parents and Teachers