In the weeks before a fatal shooting at STEM School Highlands Ranch, a 16-year-old suspect joked to friends about killing people and shooting up a school, saying it would be easy to walk inside with a gun, a prosecutor said Friday.

Alec McKinney, who faces 43 charges in connection with the shooting, also had become especially interested in Sol Pais, an 18-year-old from Miami, whose April trip to Colorado caused schools to close across the Front Range, Kristine Rolfes, a deputy district attorney in the 18th Judicial District, said. The FBI had reported that Pais was obsessed with the Columbine High School shooting. The teen girl was found dead of a self-inflicted gunshot wound on a remote Mount Evans trail.

McKinney began telling friends that people at STEM “needed to see the world for what it is,” Rolfes said. He also talked about how “everyone deserved something bad happen to them.” The teen researched Columbine and inquired about how to obtain a gun, Rolfes said.

On Friday, prosecutors continued to make their case that McKinney should continue to be prosecuted in adult court. McKinney is one of two STEM school students accused in the shooting that killed 18-year-old Kendrick Castillo and wounded eight others.

Lawyers again talked about McKinney’s drug habits and described the teen as a manipulative person who talked openly with friends about violence and who lied to medical professionals about having homicidal ideations.

Prosecutors said at least one friend pleaded with McKinney to attend Narcotics Anonymous.

“Alec made fun of that friend,” prosecutors said.

Ashley Williamson, McKinney’s therapist, testified, saying she had no idea — over the course of 27 sessions — to what extent the teen was selling and using Xanax and marijuana, snorting cocaine and drinking alcohol in the months before the shooting.

Prosecutors argued that McKinney had adequate help to deal with gender identity issues, anxiety and depression but deceived his mental health providers. McKinney’s defense team earlier presented the image of a teen who struggled with cutting, suffered from low self-esteem and grew up in a home with a violent father and an absentee mother.

On Friday, prosecutors brought in two more parents whose children were wounded in the STEM school shooting.

Lorie Jones described how her son helped tackle a second shooter, who was attacking his classroom, and then called her.

“Mom,” she said, retelling the phone call. “I’ve been involved in a school shooting. I’ve been shot a couple times, but I’m OK.”

Josh Jones leapt from his desk along with Castillo and Brendan Bialy to take down a shooter after he entered the room with a gun.

“No one wants their kid to be at school and run toward a shooter,” Lori Jones said.

After hearing from her daughter that there had been a shooting at school, Yuritzia Ojeda-Ayala kept calling her son Gerry. Finally he answered.

“Mom, I was shot in the head,” he told her.

Somehow, the 17-year-old avoided brain damage.

“The doctor said it’s a miracle,” she said.

But since May, her son has quit the soccer team, afraid to leave his own home. He still has headaches, his arm aches six months later.

“He doesn’t have the spark anymore,” Ojeda-Ayala told the court, dabbing her eyes with a tissue. “He can’t trust anybody anymore.”