Sol Pais, 18, who was infatuated with Columbine and may have been planning an attack before she killed herself, had passed background checks when she legally bought the same gun used in the 1999 massacre

The Florida teenager who was infatuated with Columbine and may have been planning an attack before she killed herself had passed background checks when she legally bought the same gun used in the 1999 massacre.

Sol Pais, 18, was found dead in the mountains just outside Denver on Wednesday morning after a massive 24-hour manhunt that shut down dozens of schools just days before the 20th anniversary of the Columbine massacre.

The FBI said Pais raised suspicion after making comments to people at home in Florida about Columbine and then buying three one-way tickets to Denver spanning three consecutive days.

The high school student flew from Miami to Denver on Monday and headed straight to the Colorado Gun Broker shop, which is located just two miles from Columbine High School.

She legally purchased a 12-gauge pump-action shotgun.

It is the same gun model that one of the teen shooters used in the deadly massacre 20 years earlier.

The gun store has since revealed that Pais underwent a full background check and was cleared to buy the weapon.

She was given clearance by both the National Instant Criminal Background Check System and the Colorado Bureau of Investigation.

'We had no reason to suspect she was a threat to either herself or anyone else,' Josh Rayburn, a spokesman for the gun store, said.

The teen was found dead in the mountains just outside Denver on Wednesday morning after a massive 24-hour manhunt that shut down dozens of schools. Pictured is her body being removed from the wooded area where she was found

The high school student flew from Miami to Denver on Monday and headed straight to the Colorado Gun Broker shop to purchase the gun

The Colorado Gun Broker shop is located just two miles from Columbine High School

Out-of-state residents who are at least 18 can buy shotguns in Colorado. Customers must provide fingerprints and pass a criminal background check.

The FBI said Pais had already bought the firearm on Monday before they even considered her a threat.

When they did launch a wide-scale manhunt for her on Tuesday after learning she had arrived in Denver, the FBI described her as 'extremely dangerous' and said she had made threats to 'commit an act of violence' after becoming fixated on the shooting massacre.

But instead of hurting anyone, Pias led authorities on a massive 24-hour manhunt that ended when she killed herself with the shotgun she had bought.

Her body was recovered on Wednesday afternoon near the Echo Lake Campground in Mt Evans.

The dozens of schools that were forced to close as a precaution during the daylong manhunt reopened on Thursday with heightened security measures.

Authorities said they will now continue looking into Pais' social media and her other other online presence as part of their investigation to ensure that she had no 'accessories' or 'accomplices'.

From the details that started trickling out on Wednesday as the manhunt continued, it became clear that Pais - who was a senior at Miami Beach High School - had been planning what authorities described as a 'pilgrimage' for weeks.

She legally purchased a 12-gauge pump-action shotgun. It is the same firearm that one of the teen gunmen - Eric Harris and Dylan Klebold (above with the gun) - used in the deadly Columbine massacre in 1999

A sawed off double barrel shotgun, ammuntion clips and an automatic pistol used in the 1999 Columbine High School shooting are displayed above

The FBI said Pais raised suspicion after making comments to people at home in Florida about Columbine and then buying three one-way tickets to Denver spanning three consecutive days

She started asking for advice last month on buying a shotgun in Colorado in a series of posts on the National Gun Forum.

'Florida resident here. I am planning a trip to Colorado in the next month or so and wanna buy a shotgun while I'm there and I was wondering what restrictions apply for me? I've found a few private sellers I might want to purchase from; is it legal for me as a Florida resident to purchase a shotgun in Colorado? I'm 18 years old too, if it's important,' she wrote on the National Gun Forum.

'The problem is i have no friends in FL who are into guns like me so it's not as fun having to do all of this alone,' she wrote in a follow up post.

A website belonging to her was filled with self-hate journal entries and contained a tribute to a Marilyn Manson song that was inspired by the high school shooting.

The site contained photocopied handwritten journal entries with multiple drawings of guns and troubling phrases like 'being alive is f**king overrated' and 'how do I pull it out of me? I'm f**king empty.'

The website also had the phrase '1999 - the nobodies' written on it. Marylin Manson wrote a song titled The Nobodies based on the 1999 shooting massacre at Columbine.

The Denver FBI office was alerted to the potential threat early Tuesday by Miami FBI agents after Pais' parents reported her missing on Monday night.

The FBI said they often receive threats around the time of the Columbine anniversary but took Pais' case seriously after realizing she had booked one-way tickets to Denver and learned of her troubling remarks to those back home about the massacre.

'We're used to threats, frankly, at Columbine,' John McDonald, security chief for Jefferson County school system, said when the manhunt was over. 'This one felt different. It was different. It certainly had our attention.'

McDonald described her trip as a 'pilgrimage' to Columbine but Pais is not believed to have been on the campus during her time in Denver.

The FBI searched the Miami Beach home where Pais lives with her parents on Tuesday night and remained outside on Wednesday

About a dozen Denver area districts called off classes for Wednesday and about a half million students were forced to stay home because authorities believed Pais could pose a threat to a school. A squad car is pictured outside Columbine High School on Wednesday

About a dozen Denver area districts called off classes for Wednesday and about a half million students were forced to stay home because authorities believed Pais could pose a threat to a school.

Authorities said she did not threaten a specific school.

Photos of the teenager were released by authorities and they warned she was 'extremely dangerous'.

Her body was found in the mountains after investigators got a tip from the ride-share driver who took her there.

She had also reportedly been spotted by witnesses running around naked with the shotgun.

In Pais' hometown in Florida, Surfside Police Chief Julio Yero asked that the family be given 'privacy and a little time to grieve.'

'This family contributed greatly to this investigation from the very onset. They provided valuable information that led us to Colorado and a lot of things that assisted in preventing maybe more loss of life,' Yero said.

The FBI searched the Miami Beach home where Pais lived with her parents on Tuesday night and remained outside on Wednesday.

Classmates at Miami Beach High School were shocked to learn that Pais was the person authorities in Colorado had been searching for.

Pais, who was taking AP and honor roll classes, was described by her classmates as quiet and smart.