DOUGLAS COUNTY, Colo. — The 16-year-old student who was charged as an adult in connection with the deadly May 2019 shooting at STEM School Highlands Ranch on Friday pleaded guilty to 17 charges, 14 of them felonies, during an arraignment hearing.

Alec McKinney pleaded guilty to the following charges:

  • First-degree murder for the death of Kendrick Castillo
  • Conspiracy to commit first-degree murder after deliberation
  • Six counts of attempted murder after deliberation
  • Attempted murder extreme indifference 
  • Second-degree assault 
  • Conspiracy to commit arson
  • Conspiracy to commit burglary
  • Conspiracy to commit criminal mischief
  • Possession of a weapon on school grounds
  • Possession of a handgun by a juvenile
  • Two crime-of-violence sentence enhancers

McKinney and his co-defendant, 19-year-old Devon Erickson, are accused in the May 7 shooting that resulted in the death of 18-year-old Kendrick Castillo. Castillo is lauded as a hero for joining other classmates to rush one of the two gunmen. 

Eight others were also shot. Two of them were injured by a private security guard who helped detain one of the teen suspects.

RELATED: STEM School Highlands Ranch security guard to enter diversion program after shooting 2 students

"This is the road to healing,"  said John Castillo, Kendrick Castillo's father. "It's not healing just for my wife and I but the other families that were affected. You know nobody is a winner out of this."

Both suspects were charged with 46 separate counts, including two counts of first-degree murder, one count of conspiracy to commit first-degree murder and 31 counts of attempted first-degree murder. Those charges are still pending against the older suspect.

RELATED: 'We miss him so much': STEM shooting victim's mom testifies in final day of hearing for younger suspect

In December, following a week-long reverse transfer hearing, a Douglas County judge ruled that McKinney's case would move forward in adult court. His defense had argued to move it back to juvenile court.

Kendrick Castillo's parents attended every day of that hearing. 

"We went through seven days of a reverse transfer hearing that was brutal," John Castillo said. "I can only tell you that every day was tougher than I ever thought, and I can't imagine going through trial."

At Friday's hearing, he wiped away tears several times as he thought about his son.

"I'm sitting in there thinking of him and doing things together, and at the end of the day, no matter what happens in the courtroom, the results are always going to be the same," John Castillo said.

RELATED: Younger STEM School shooting suspect to be tried as adult, judge rules

Due to his age at the time of the incident, McKinney will automatically be sentenced to life in prison with the possibility of parole after 40 years related to the first-degree murder charges. Under Colorado law, defendants who commit crimes as juveniles cannot be sentenced to life without the possibility of parole.

In addition to that sentence, he faces 408 years for the other charges, but the exact amount of time is up to the discretion of the judge at sentencing, which is set for May 18.

"I thank God that he entered into a guilty plea," John Castillo said. "It made life a little bit easier on families and ourselves, so we can move onto the next perpetrator."

RELATED: Older suspect in STEM School shooting pleads not guilty

Last month, Erickson pleaded not guilty, and his trial was scheduled for May 26. Because of his age at the time of the crime, prosecutors could choose to seek the death penalty. If they don't, he would have a mandatory sentence of life in prison.

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