(CNN) - Five months before Tuesday's fatal shooting at a Colorado charter school, a district official urged the school's administration to investigate allegations of violence, sexual assault and campus bullying that an anonymous parent feared could lead to "a repeat of Columbine," according to a school district letter obtained by CNN.
The parent called a member of the county Board of Education to express "concerns about student violence due to a high-pressure environment," according to the letter. The parent referenced an alleged bomb threat and other student clashes as evidence that the school could become the site of another Columbine, the infamous school shooting that occurred 20 years ago, only around seven miles from STEM School Highlands Ranch.
Douglas County School District official Daniel Winsor wrote the letter in December to STEM's executive director. He noted that the parent complained that "many students are suicidal and violent in school. Several students have reported sexual assault in school and that nothing is being done."
Winsor asked the school's executive director to "investigate the allegations ... determine their legitimacy and to take any remedial action that may be appropriate."
"The concerns expressed by this individual are very serious and need to be looked into to the extent possible. Please keep (the district) apprised of your investigation and conclusions," wrote Winsor, the district's director of choice programming.
In a February letter to parents, Penelope Eucker, the executive director of STEM, the K-12 charter school where one student was killed and eight others were injured on Tuesday, disputed many of the anonymous parent's claims of campus problems.
Eucker and the STEM board president wrote to parents, saying the allegations against the school administration had been investigated and there was no evidence to support the anonymous claims.
Their letter, a copy of which was also obtained by CNN, did not address the reported concerns about the high-pressure environment resulting in student violence.
They wrote that the school had gone so far as to file a lawsuit against "Jane Doe" for spreading what they called "defamatory statements" about the school.
"We want you to know the depth of this depravity and apologize if you find this as offensive as we did," they wrote.
Court documents confirm this lawsuit was filed in January 2019.
Winsor could not be immediately reached for comment. CNN has not been able to verify the parent's allegations, including the alleged bomb threat, with law enforcement.
On Thursday, Eucker provided CNN a statement via a public relations firm, saying that following the parent's complaint, STEM reached out to all of the school's parents "in the hopes that any student or family member with knowledge of the allegations would confidentially share that information." She said that the school did not receive any responses with information about the allegations.
"The safety and wellbeing of our students and staff is our highest priority," she said in the statement, noting that "like any school with more than 1,800 students, we receive complaints, all of which we take seriously and investigate promptly."
She did not comment on the lawsuit.
There were other signs of tensions at the school.
The school district sent a letter to STEM's board of directors last year about "legal costs for special education matters" saying it had received more complaints since the beginning of the previous school year than any other charter school in the district -- including one that resulted in a financial settlement agreement and two that resulted in corrective action.
Another 2018 letter from the county Board of Education said it had "significant concerns" about STEM's compliance with the charter school contract and legal requirements, and questioned its willingness to serve students with disabilities. It also cited "ineffective leadership," saying, "the tenor of the comments at our meetings suggests that the relationship between STEM and some of its parents is irretrievably damaged."
An online petition signed by multiple parents and a post on a Facebook page for the school district community also expressed concerns about the leadership of the school. And minutes from a "School Accountability Committee" meeting at the school describe "a small group of people who speak against STEM."
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Correction: A previous version of this story stated that the district filed a defamation suit against the parent. The suit was filed by STEM School Highlands Ranch.
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