More than 100 copycat plots and attacks have happened in the nearly 20 years since the Columbine shooting, according to a report published Wednesday. 

In addition to the 100 plans and attacks found the by progressive magazine Mother Jones, there have also reportedly been dozens of others that were not widely reported.

According to the magazine, people who plan or commit these type of attacks can be motivated by media coverage, although it says, citing an FBI study, that grievances and behavioral issues are the main reasons for such shootings and shooting plots.

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One threat assessment expert says the regular reference to shootings as “Columbine-style” has also contributed to the issue of copycats. 

“Every single school shooting, the media calls it a Columbine-style attack,” said threat assessment expert John McDonald, who runs security for 157 schools Colorado’s Jefferson County, including Columbine High School.

“We’ve taken more guns off kids this year than any other year, and it’s not just here,” he told the magazine. “My counterparts I’m talking to around the country are seeing the same thing.”

The school district has seen an increase in threat cases in recent years, recording more than 800 cases this school year, 46 of which were found serious enough to be handled by Jefferson Country's threat assessment team. 

The report comes just before the 20th anniversary of the massacre in Colorado. On April 20, 1999, 12 students and a teacher were killed at Columbine High School by two students who later killed themselves.

It also comes as Denver-area schools were closed Wednesday as authorities launched a manhunt for a woman they say is dangerous and has made “credible threats” days before the 20th anniversary of the shooting.

Police are searching for 18-year-old Sol Pais, who allegedly traveled from Miami to Colorado because she is “infatuated” with the school shooting, USA Today reported.