Just days after a mass shooting claimed nine lives at Umpqua Community College in Roseburg, Ore., authorities in Northern California said they uncovered a plot to shoot teachers and students at a high school in Tuolumne.

Police have arrested four teenagers who, officials say, planned to attack Summerville High School; the four have been charged with conspiracy to commit an assault with deadly weapons, according to the Associated Press.

Tuolumne County Sheriff Jim Mele told the AP that plans for the attack were in the early stages but were “very detailed in nature and included the names of victims, locations and methods in which the plan was to be carried out.”

Investigators said the suspects were also attempting to obtain weapons for use in the attack.

“They were going to come on campus and shoot and kill as many people as possible at the campus,” Mele told NBC affiliate KCRA.

Mele said the four students, all male, have admitted to the plot, which was scheduled to take place during a school event, according to KCRA.

Investigators learned of the plot Wednesday after school officials called to report students making threats toward faculty and staff, according to ABC affiliate KXTV. The administrators had been alerted by students, police said, that some of their classmates were behaving suspiciously.

“As each one of them was identified they were removed from campus,” Robert Griffith, superintendent of the Summerville Union High School District, told the station. “Their parents were called.”

Investigators said they also plan to call the parents of students named on the hit list, according to KCRA. The idea that they might receive a call from police about the list was almost too much to bear for some parents.

“The thought about my daughter being on that list makes me sick,” Kristin Wilson told KCRA. “Do I want to know? Do I not? I don’t know.”

The Summerville plot was foiled 24 before hours before a heavily armed 26-year-old walked into Umpqua Community College in Oregon and killed nine people, before taking his own life. In Tuolumne County, the Oregon massacre served to remind officials and parents how close their community came to disaster.

“It is clear from past history, such as Columbine and Sandy Hook, as well as other recent events in Oregon, that children are willing and capable of planning and carrying out acts of violence against fellow students and teachers on school grounds,” Eric Hovatter, Tuolumne County assistant district attorney, told KCRA. “While it is easy to say that can never happen in Tuolumne County, the public and local law enforcement must be vigilant, as they were here.”

As students prepared to return to the high school, Griffith, the superintendent, spent part of his Sunday on the Summerville campus, according to Sacramento’s CBS affiliate, “planning for the tough week ahead of bringing back a sense of normalcy to campus.”

“Just to bring some, you know, calm to some fearful people,” Griffith told the station.

Easier said than done.

“I wouldn’t think that kind of thing would happen in this kind of school, or in this kind of town,” Summerville sophomore Makayla Armbright told KCRA, adding she doesn’t plan to go return to school on Monday.

Her mother, Angelia Blout, “supports that decision,” the station reported.

“That’s something that every parent worries about,” she said. “Is it going to be safe at school?”

This post, originally published on Oct. 4, has been updated. 

MORE READING: 

Police arrest gunman accused of killing Dallas dentist in murder-for-hire plot

After killing bear cub with homemade spear, homeless man claims he was defending children