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DOUGLAS COUNTY, Colo. (KDVR) — A jury of 12 people and four alternates has been selected in the trial against accused STEM School shooter Devon Erickson. Opening arguments began Thursday.

“In this room is terror,” said prosecutor George Brauchler. “In this room is every parent and every teacher’s worst nightmare. In this room are bullets and students’ blood, and the body of a hero.”

Brauchler said Erickson had many opportunities to stop the shooting on May 7, 2019, but he didn’t.

Brauchler showed security camera video from inside the school. On it, Erickson and Alec McKinney walk into the school with four concealed guns and wave to a secretary.

“Before they part, they give each other a quick bro hug and a fist bump,” Brauchler said.

Erickson is facing 46 counts, including two first-degree murder charges and 31 first-degree attempted murder charges.

Erickson’s defense attorney, Julia Stancil, tried to paint a different picture of him.

“This is a case about mental health,” Stancil said. “It’s a case about manipulation. It’s a case about how Devon Erickson’s home life came undone at critical time at the end of high school.

“It’s about how a vulnerable kid Devon Erickson gets roped into a psychotic cult play, by a schizophrenic, homicidal sick kid, named Alec McKinney,” Stancil said.

Kendrick Castillo, 18, was the student killed in the shooting. He has been hailed a hero for joining other classmates and rushing Erickson during the attack, possibly saving lives and others from being injured.

Stancil called McKinney the puppet-master behind the shooting and said Erickson did not mean to shoot Castillo. She said the .45-caliber Glock fired when Castillo and other students tackled him.

“He did not intend to do this,” Stancil said of Erickson. “He’s not evil. He didn’t hate STEM. He didn’t hate the world, and he’s not guilty of first-degree premeditated murder.”

Erickson was in court for all of the opening statements. He wore a blue suit with a tie and his hair was trim. He was attentive to both attorneys and often looked down during the most intense video and audio.

Another student involved in the shooting, Alec McKinney, pleaded guilty last year to charges stemming from the shooting. He has been sentenced to life in prison with the possibility for parole in 40 years.

Erickson’s trial is scheduled through June 25 in Douglas County District Court.

Disclaimer: The trial contains profane language when referencing videos and texts between the suspects leading up to the shooting. You can watch the full opening statements in the video below.