DENVER — After the search for a Florida woman who the FBI believed was making credible threats prompted closures at Colorado’s largest school districts Wednesday, class are back in session on Thursday – albeit with increased security.

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The 18-year-old subject of the multi-agency manhunt, was found dead in the Mt. Evans area on Wednesday morning. Law enforcement said she was found with the shotgun she purchased near Littleton after arriving in Denver on Monday morning, and is believed to have taken her own life.

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About a thousand schools canceled class while police searched for the woman, who the FBI first became aware of on Tuesday morning following a tip from their counterparts in Miami, leading to a lockout at multiple Jefferson County schools that quickly spread to districts throughout the Denver metro area.

The cancellations began just before midnight on Tuesday, with Cherry Creek Schools and Douglas County Schools being the first to post closures. Other districts – including Denver, Aurora, Jefferson County, Douglas County, Englewood, Littleton and more – followed early Wednesday morning.

This meant that more than 500,000 students across the Front Range were out of school on Wednesday.

It will not entirely be business as normal when they return to class on Thursday though.

In a letter to parents, Jeffco Public Schools said there will be “heightened safety and security measures in place.”

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This was a sentiment also echoed by the Douglas County School District, Denver Public Schools and others.

The timing of the threats comes just a few days before the April 20 – which will mark 20 years since 12 students and a teacher were killed at Columbine High School.

In a bulletin distributed to law enforcement, the FBI described the Florida woman they were looking for as “infatuated” with the attack. Since, the agency has not provided details about the exact nature of her threats, and said they were not directed at a specific school.

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