Sixteen-year-old Sienna Johnson kept a journal filled with angst-ridden poetry and intricate, often macabre, drawings.

“I feel very stranded and alone,” she wrote in one entry. On the same page, sideways and near the margins, she had scribbled and highlighted the words “They’re still after you.”

And above that, in a corner near the notebook’s spiral coils: “It’s all my fault.”

Were these the harmless reflections of a high school student simply going through a tumultuous adolescence? Or did they point to dangerous inclinations?

Where Johnson comes from, in Highlands Ranch, Colo., the authorities don’t take chances.

Just to the west of the affluent Denver suburb is a neighbor with a dark reputation. More than 15 years ago, two armed adolescent males entered Jefferson County’s Columbine High School and opened fire, killing 12 fellow students and a teacher before fatally turning their guns on themselves.

The massacre that continues to haunt the country and ignite disturbed minds now looms over nearby Highlands Ranch, as two teenage girls have been charged on two counts of conspiracy to commit first-degree murder in an alleged plot reminiscent of what once took place less than 10 miles away.

Brooke Higgins, 16, was charged this Thursday; Johnson last week. Both are students at Mountain Vista High School, where prosecutors say they were planning to execute a mass shooting, according to the Denver Post.

While Higgins’s and Johnson’s lawyers argue that the allegations against them are exaggerated and amount to “nothing unusual,” prosecutors have laid out a chilling trail of online searches, journal entries and social media postings that they say proves real criminal intent.

“They were friends, they hung out outside school, and prior to this had said things individually about shooting up the school, then when they got together they put that plan into motion,” district attorney Jason Siers told the court on Thursday, the Guardian reported.

Dagny Van der Jagt, Higgins’s lawyer, countered that the 16-year-old is guilty of no more than a “thought crime.” She also tried to distance her client from Johnson, arguing that the two were barely friends and are being linked by “weak circumstantial inferences.”

Police were tipped off to the girls’ potential plans through an anonymous texting hotline.

“I think the text message and the information we obtained through our investigation saved lives, for sure, given the severity of the situation,” Douglas County Sheriff Tony Spurlock told the Denver Post.

The case is unusual. Very few mass shootings are perpetrated by women. Among the 160 active-shooter incidents logged by the FBI between 2000 and 2013, only six of the shooters were female.

According to the Denver Post, prosecutors said Higgins had scoured the Internet for ways to procure firearms as a minor, seeking information on female mass shooters and buying weapons at gun shows.

She also allegedly wrote in a journal that she wished she could have participated in the Columbine shootings. Likewise, Johnson supposedly referenced in her journal “Natural Born Killers,” a satirical film about two people with traumatic childhoods who become mass murderers.

The film, with a screenplay written by Quentin Tarantino, has been linked to a few real-life crimes. Dylan Klebold, one of the Columbine shooters, indicated that he was a fan of “Natural Born Killers” in a journal entry.

Higgins and Johnson, who have been in jail since Dec. 12, are being held on $1 million bail because they have been deemed a potential threat to the community.

According to the Guardian, authorities said Johnson made detailed maps of her high school that outlined the locations of specific individuals, such as law enforcement officers assigned to guard the campus.

In the days leading up to Christmas, around the time that the alleged plot would have borne fruit, Johnson allegedly practiced using BB guns. Upon her arrest, authorities said, she told them she would return to planning a shooting if she were released.

“The idea that the incident at Columbine is to be admired, that the people who did that are gods or heroes …” district judge Paul King said in court in Castle Rock, Colo., on Thursday, the Guardian reported. “There are parents in this city that want to make sure their kids are protected.”

King acknowledged that the evidence presented by prosecutors is troubling.

“They are more than problematic given the circumstances,” he said, the Denver Post reported.

Still, Higgins’s and Johnson’s youth has been a subject of lengthy debate. While they are slated to be tried as adults, both high school students’ lawyers will argue in hearings that their cases should be sent back to juvenile court.

The possibility that the girls may not end up being tried as adults has prompted King to keep their arrest records sealed despite attempts by local media to unseal the documents.

Some handwritten pages of Johnson’s journal, uploaded to her Weebly site, reveal the fraught thought processes of a teenager who described herself as having a childhood that  “turned sour.”

According to a biography on her “About page,” Johnson’s parents divorced when she was 2 years old. She “grew up with a lot of pain,” constantly moving with her mother and sister, before settling down in South Carolina for a briefly “perfect life” before moving again to Colorado, where her father lived.

“After we moved, things were just really difficult. I was angry because I didn’t have the ‘normal’ family and I was always getting shuffled around between my mom’s and dad’s,” Johnson wrote, noting that she spent most of her time on creative endeavors, such as music (guitar and drums), writing and drawing, for which she won awards in middle school. “I still put all my time and energy into the things I enjoy most and hope to be the best I can be.”

The “Art” page features blood-splattered figures, drawn and painted with a high degree of technical skill. One shows a man pointing a gun to his head; another depicts a skeletal woman lying in a pool of red, grasping at her neck.

The Guardian reported that, according to prosecutors, Johnson wrote in her diary last year that she had met someone “who’s got what it takes to … make this school a living f—king nightmare.”

She allegedly concluded: “God, Brooke and me will be unstoppable.”

Darrell Scott, whose daughter died in the Columbine shooting, told KUSA that Johnson’s writing points to desperation.

“This young girl was really crying out, wasn’t she?” he said. “I think a lot of the violence that we see is a cry for help and a cry to be recognized. That doesn’t excuse any of the horrible things that they do, but if we paint them as monsters, if we paint them as inhuman, we’ll never be able to help them.”

More from Morning Mix: