A criminologist at Regis University said there appeared to be a lot of red flags in 16-year-old Sienna Johnson's case and added she likely fantasized about committing the crime.
Johnson is being charged as an adult in the alleged murder plot at Mountain Vista High School in Douglas County. She faces two felony counts of conspiracy to commit murder.
"It's spooky, it scares a lot of people," said Don Lindley, chair of the criminology department.
In Instagram photos, Johnson looks like any other teenager. However, Lindley said new details revealed in court on Tuesday are indicators of murder-prone kids.
"It's psychosomatic, it's not psychopathic but it's bordering on that," said Lindley.
Prosecutors said in court Tuesday that Johnson had harmed animals in the past and kept a journal of disturbing drawings and entries.
"It's just one more step between harming an animal and harming a human -- there's a very gray line in between," said Lindley.
Prosecutors also said Johnson had a very detailed map for the day of the attack and bought a BB-gun for target practice.
All things Lindley said showed Johnson was close to committing the alleged murder plot.
"It sounds like she was at the second stage, she fantasized about it, she started acting on it and it was prevented," he said. "The next step would have been, [that] she would have done it."
Prosecutors also said Johnson showed no remorse and told a detective if she got out -- she would try the plot again.
Johnson is being held on a $1 million bond.
The other teen arrested in the case will undergo a mental health evaluation before any charges are filed.