ABC News February 7, 2020

16-year-old STEM school shooting suspect pleads guilty to murder

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A 16-year-old accused in a Colorado school shooting pleaded guilty to multiple charges, including murder, on Friday.

Two teenagers, Alec McKinney and Devon Erickson, were arrested after allegedly opening fire at the STEM School Highlands Ranch near Denver on May 7, 2019.

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Kendrick Castillo, an 18-year-old who tried to confront the shooters, was killed. Multiple students were injured.

Courtney Harper/AP, FILE
In this May 7, 2019 file photo, police officers and students are seen outside STEM School Highlands Ranch, a charter middle school in the Denver suburb of Highlands Ranch, Colo.

McKinney -- who was born biologically female but identifies as male -- pleaded guilty Friday to multiple charges, including first-degree murder, attempted murder and conspiracy to commit first-degree murder after deliberation.

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The mandatory minimum sentence is life with the possibility of parole after 40 years minus earned time, prosecutors said.

McKinney's sentencing is set for May 18, prosecutors said.

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Erickson, 18, pleaded not guilty. He has a trial scheduled for May, The Denver Post reported.