What to Know Police say they thwarted a high school girl's imminent threat to bomb her high school and shoot people.

Nicole Cevario, 18, kept a diary with detailed plans on how she would attack Catoctin High School in Thurmont, Maryland, police say.

She will be charged with a crime once she is released from a hospital.

A female high school student had immediate plans to bomb her school in Frederick County, Maryland, and shoot students and teachers, police say.

Nicole Cevario, 18, stockpiled bomb-making materials and had a shotgun to attack Catoctin High School on April 5, the Frederick County Sheriff's Office said Monday. She wrote about her plans in detail in a diary her father found.

Police believe the diary entries were not empty threats, Sheriff Charles A. Jenkins said at a news conference.

"We felt this was going to be carried out. There is no doubt in our minds that we diverted a disaster up there," he said.

Cevario "had the means and equipment to have caused a significant life safety event” at the school, police said in a statement.

Frederick County Sheriff's Office

Police learned of Cevario's plot after her father read her diary and called the school. Within hours, the honor student was pulled out of a classroom and involuntarily taken to a hospital for a psychological evaluation.

Police searched Cevario's home in Thurmont, Maryland, and found weapons and the diary. In the home, police say they found a 12-gauge shotgun with ammunition and bomb-making materials including pipes with end caps, shrapnel, fireworks, magnesium tape and fuse material. The gun and other items were purchased legally, police said.

In the diary, police say Cevario "spelled out a detailed shooting event that she planned to execute on a specific date in April," police said.

Officials later said that date was April 5. It was not immediately clear whether that date had any significance.

The diary showed the high schooler, who had been taking college classes in criminal justice, had been planning the attack for some time, police said. She compiled information on the school's emergency procedures and the school resource deputy on duty.

"The journal was very detailed, including a time line that revealed how she was going to execute the plot, and her expectations at each stage of the event," police said.

Officials say Cevario acted alone and never took a weapon or explosive device to the school. It was clear she had mental health issues, the sheriff's office said.

"Obviously, this was a student who needed some intervention and some help, and I think the silver lining is she's going to get the help she needs now," Frederick County Public Schools spokesman Michael Doerrer said.

The tip police received from Cevario's father may have saved lives, officials said.

"The Sheriff’s Office is extremely appreciative of the parent’s actions in bringing this potentially deadly incident to the proper authority’s attention, promptly, so that a positive conclusion could be achieved," the statement said.

The U.S. Bureau of Alcohol, Tobacco and Firearms and the Maryand State Fire Marshal's bomb squad assisted the sheriff's office.

The school's principal assured parents that students are secure there.

"We keep our school safe, and we will continue to work together as a community to keep it safe," Principal Bernie Quesada said in a letter sent Monday.

Counselors were available at the school.

Once Cevario is released from the hospital, she will be charged with possession of explosive and incendiary material with intent to create a destructive device.

Law enforcement and school officials said they had no sign Cevario had any problem.

Anyone with information for police is asked to call 301-600-2583.