Like any American school, Mooresville High School in Indiana had long since set up security protocols and mental health services to try to prevent violence on campus.

Yet those policies didn’t fully prepare them psychologically for the arrest in February of an 18-year-old senior accused of planning “Parkland part two.”

“Our reaction – and the community’s – was one of shock,” Matt Saner, the president of the Mooresville Schools board of trustees, told CNN in an email. “These aren’t just nameless students that we are responsible for keeping safe, these are our neighbors. Our friends. Our family. Our own kids.”

The Mooresville student’s arrest was just one of the many instances around the country, from New York City to Washington state, in which security measures worked as intended, thwarting a potential explosion of violence.

CNN and other media outlets have long explored the aftermath of horrific school shootings: The funerals, the physical and psychic damage to survivors, the investigations into what went wrong and the efforts to rebuild.

Less explored is what happens when a potential school shooting is successfully thwarted – how the community reacts to the near-tragedy and the lessons learned from a successful intervention.

The Mooresville student, Trinity Shockley, now 19, is expected to plead guilty to conspiracy to commit murder on Monday in an Indiana courtroom as part of a plea deal with prosecutors. The “contested” plea hearing – the debate is over the length of the sentence – will include presentations of evidence, prosecutors said.

Shockley’s attorney declined to comment.

Ahead of the hearing, CNN reviewed the available information about the case and spoke with school officials to better understand what happened and the lessons for other school districts.

“After going through something this serious – and knowing how fortunate we were to avoid a tragedy – my biggest advice to other districts is to learn everything you can from the experience and share those lessons with others,” said Jake Allen, the superintendent of Mooresville Schools.

“It is critical to take an honest, comprehensive look at what worked well and what did not.”

Shockley, then an 18-year-old senior at Mooresville High, was arrested in February and accused of planning to carry out a mass shooting at the school on Valentine’s Day. The arrest stemmed from an anonymous tip to law enforcement and a concerning conversation with a school counselor, according to an affidavit obtained by CNN affiliate WISH.

The tip to the Sandy Hook tip line on February 11 stated Shockley had access to an AR-15 rifle, had just ordered a bulletproof vest and admired Nikolas Cruz, the gunman who murdered 17 people at Marjory Stoneman Douglas High School in Parkland, Florida, officials said.

“Parkland part two,” Shockley wrote in a Discord chat. “I’ve been planning this for a YEAR.”

The FBI traced the IP address associated with the Discord account back to Shockley, and the tip was forwarded to local law enforcement, the affidavit says.

Earlier that same day, Shockley “asked to speak with a school counselor” and at that meeting spoke about an “obsession” and sexual attraction to the Parkland shooter, including a heart-locket necklace with his photo, according to the affidavit. The counselor notified the school administration and a response plan was scheduled for prior to the next school day, Mooresville Schools said.

The following day, a SWAT team surrounded Shockley’s home and took the student in for questioning before police executed a search warrant and found in Shockley’s bedroom further evidence of a fascination with mass shooters, according to the affidavit.

Shockley told police in an interview about having a “breakdown” at school on February 11 because of the student’s mother’s recent death, the affidavit states. Shockley spoke extensively about a shooting plan and expressed a deep interest in school shootings, according to the affidavit.

At the end of the interview, Shockley was placed in restraints and taken into custody, the affidavit states.

Shockley is charged under the name Trinity but is transgender and goes by the name Jamie, according to the affidavit.

Last month, Shockley agreed to plead guilty to conspiracy to commit murder as part of a plea deal and will be sentenced to 20 years in prison with 12.5 years in custody and the rest suspended. The plea also states Shockley cannot possess a gun, set foot on school property, or “be allowed to research, look at or view in any way materials relating to school shooters,” the agreement states.

In an email to CNN, several Mooresville school officials said the school’s safety policies worked as intended. They particularly praised the counselor’s decision to report the concerning conversation with the student and the school’s relationships with law enforcement.

“The information the student shared with a counselor, along with the FBI tip, all surfaced within hours,” Saner said. “Our staff responded without hesitation, exactly the way they’ve trained and prepared for, and our partnership with law enforcement made a tremendous difference in preventing something far worse.

“I was incredibly proud of how quickly and calmly our staff acted, and grateful for how fast law enforcement was able to act,” he added.

Wes Upton, the Mooresville High School principal, said the school had been meeting monthly with local agencies, including fire, police, EMS and mental health providers. The student’s arrest added “reassurance to our efforts on that front,” he said.

“In February, our administrators and local law enforcement worked together exactly as our safety protocols are designed to function,” he said.

Speaking with concerned parents, students and the public was another challenge. In the aftermath of the arrest, “transparency and clear communication” with the community was “critical,” Saner said.

“The amount of positive feedback we have received from families, and the outpouring of support from the broader community, truly highlights how close-knit and caring our town is,” he said.

“Our community has expressed confidence in the processes we have in place,” Upton said.

Principal’s one regret and ways to improve

Shockley had sought mental health resources from the school as a freshman and had expressed suicidal ideation, a school official told investigators, according to the affidavit.

The school official said when Shockley asked for help, the student’s father denied access to the resources because he “did not believe in mental health treatment and did not take his daughter’s conditions seriously,” the affidavit stated. Shockley signed up for mental health services in November 2024, two weeks after turning 18, the document says.

CNN has reached out to Timothy Shockley for comment.

Upton told CNN the counselor acted appropriately after the concerning conversation with Shockley.

“We are all thankful to have someone who saw concerning signs and spoke up right away,” he said. “We have a well-trained threat assessment team and our staff members know who to contact with concerns. Our counselor followed the threat assessment protocol, which helped us to get our plan in motion prior to our contact with law enforcement.”

Still, he expressed regret that school officials couldn’t better help the student earlier.

“Our counselors and administrators have all expressed that we wish we could have provided the student with the mental health support we recommended to her and her family long before this incident,” he said. “Unfortunately, the school could not get parent permission to provide those services, despite the student asking for help after experiencing traumatic events. We will never know what those services could have changed.”

In addition, Saner said, the district, school, and law enforcement conducted a debrief reviewing the entire incident. They identified “valuable insights” into “navigating” the many different law enforcement jurisdictions as well as how to handle sensitive information while keeping the public informed.

“Every event teaches you something, and the board fully supports our administrators’ ongoing efforts to strengthen threat prevention and keep our schools as safe as possible,” Saner said.

Allen, the superintendent, offered recommendations to other school districts in a similar position: Examine what worked and what didn’t, share takeaways with others and don’t forget about the human side of it all.

“Finally, the aftermath isn’t just about systems and procedures, it’s about people. Make plans to support your students, your staff, your families, and your community as you move forward,” he said. “At the end of the day, we were prepared as well as we could have been and extremely fortunate and blessed to have avoided what could have been a devastating event.”