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A Douglas County Sheriff's Office patrol vehicle outside of STEM School Highlands Ranch following a shooting that left one student dead and eight others wounded on Tuesday, May 7, 2019. (Jesse Paul, The Colorado Sun)

The trial of one of two former STEM School Highlands Ranch students accused of attacking the school in 2019, killing one classmate and injuring six others, opened Thursday with the sound of a teacher’s frantic breathing.

“There’s a shooting at STEM School Highlands Ranch!” the teacher, Erin Christian, cried in a call to 911 on the day of the attack, May 7, 2019, as she huddled next door to the classroom where the shots were fired. 

Her voice echoed across a Douglas County courtroom Thursday, as prosecutor George Brauchler played the audio recording for jurors.

“Erin,” the 911 operator calmly told the teacher, “I want you to do exactly what you’ve been trained to do.”

Questions about what led to that moment and who is to blame for the shooting in Room 107 will be debated over the next month in District Court Judge Theresa Slade’s courtroom. But already on Thursday, as prosecutors and defense attorneys gave their opening statements, the fault lines became clear.

To prosecutors, the now-20-year-old man on trial, Devon Erickson, is a calculating, lying killer who conspired with another student to commit the attack and then concoct a story in which he portrayed himself as a victim, too.

“This plan is as diabolical as it is deadly,” Brauchler said. 

Only the intervention of several students, including Kendrick Castillo, who was killed trying to stop the shooting, prevented it from being worse.

Kendrick’s parents, John and Maria Castillo, sat in the courtroom during opening statements, visibly shaken by the narratives described by both the prosecution and defense. Also in the courtroom were other victims of the attack, including students and staff who were in Room 107 that day.

In one corner of the courtroom, Erickson’s family also listened to the start of the trial. Throughout the afternoon’s hearing, soft sobs could be heard from both sides of the room. 

To defense attorneys, Erickson is a “normal, happy, funny kid” who lost his way amid a vortex of drug abuse, sleep deprivation and family crisis. Attorney Julia Stancil said Erickson, in a fog of intoxication, intended to stop the attack, not participate in it. She described the other student involved, Alec McKinney, as a “puppet master” who manipulated Erickson into a “psychotic cult play.”

“Devon Erickson did not intend to kill,” she told jurors. “Devon Erickson is not a demon. He’s not a monster.”

McKinney and Erickson walked into the STEM School on the day of the attack carrying two bags holding a total of four guns. Castillo was shot as he charged Erickson — prosecutors contend Erickson fired intentionally, the defense argues it was accidental.

Brauchler identified by name six more students who were shot during the attack, four by McKinney and two allegedly by Erickson. Two other students also suffered bullet wounds after being shot mistakenly by a security guard.

Erin Triplett, right, hugs her daughter, who is an eighth grader at STEM Highlands Ranch School after the girl was escorted from the school after two students allegedly shot at least eight other kids there on May 7, 2019, in Highlands Ranch, Colorado. (John Leyba, Special to The Colorado Sun)

McKinney, who was 16 at the time of the attack, pleaded guilty last year to 17 counts in connection with the case, including first-degree murder. He may be a key witness for prosecutors during Erickson’s trial. McKinney was sentenced to life in prison with a chance of parole after 40 years.

Erickson faces 46 charges, including first-degree murder and attempted first-degree murder. If convicted of first-degree murder, he would be automatically sentenced to life in prison without the possibility of parole.

Brauchler’s opening statements gave jurors a preview of a case that will be loaded with wrenching testimony by students, teachers and school counselors and nurses. He told jurors they will hear from students who wrestled McKinney and Erickson to the ground and pried a gun out of Erickson’s hand. They will hear from a school nurse who saw Erickson just prior to the attack, one of numerous opportunities Brauchler said Erickson had to warn someone of what was to come but didn’t.

During his opening statement, Brauchler played surveillance videos taken from the school’s hallways, one showing McKinney and Erickson parting ways with a fist bump as they moved into position for the attack, another showing students running in terror after shots were fired.

He played two Snapchat videos taken by McKinney on the day of the shooting — videos that Brauchler said were staged to make it look as if Erickson was being forced to participate, part of what Brauchler called a premeditated “victim-hero story” that Erickson hoped to tell to spare himself from accountability for the shooting.

Kendrick Castillo. (Colorado State Patrol handout)

“When he’s finally subdued and only when he’s finally subdued — only then does he say, ‘Alec made me do it,’” Brauchler said.

Brauchler said he will implore jurors to “hold him accountable for what he did in helping to try to murder a classroom full of students.”

But in the defense’s hands, that evidence held different meaning. 

The videos, Stancil argued, show how McKinney actually was bullying Erickson, whom she said was clearly impaired after having spent the previous night and morning doing drugs — drugs she said McKinney introduced Erickson to.

She said the defense intends to call expert witnesses to testify to the effects of heavy drug use and sleep deprivation. Another witness will talk about the science of human reflexes and accidental trigger pulls. Another will testify to the impaired decision-making abilities of teens, part of a defense argument that Erickson tried to stop the attack but couldn’t because he was too impaired.

“He wanted to stop it,” Stancil said. “Not that his actions make sense. Because there’s no way to make sense out of this. But that’s what he was thinking at the time.”

And Stancil indicated that the defense will heavily attack the credibility of McKinney, who she said made a deal with prosecutors to pin the blame on Erickson.

“The government has made a deal with the sick, psychotic, schizophrenic kid,” Stancil said, referring to McKinney.

Witness testimony in the trial is expected to resume Friday morning. Access to the courtroom is limited due to the coronavirus pandemic, but the public can watch the proceedings via a live stream link available on the court’s website.

The trial is expected to run into late June.

Elliott Wenzler wrote about politics, water, housing, and other topics for The Colorado Sun from October 2022 through September 2023. She has covered community issues in Colorado since 2019, including for Colorado Community Media. She has been...

John Ingold is a co-founder of The Colorado Sun and a reporter currently specializing in health care coverage. Born and raised in Colorado Springs, John spent 18 years working at The Denver Post. Prior to that, he held internships at...