kuzma/iStockBy CLAYTON SANDELL and IVAN PEREIRA, ABC NEWS

(DENVER) — A 17-year-old transgender teen who told investigators he launched a deadly school shooting in retaliation for being bullied over his gender identity has been sentenced to life in prison with the possibility of parole.

Alec McKinney was sentenced Friday following impassioned, emotional statements from nearly two dozen teachers, students and family members. McKinney and fellow student Devon Erickson, 19, were accused of opening fire at STEM School Highlands Ranch in a suburb south of Denver on May 7, 2019.

McKinney, who couldn’t face the death penalty because he was a minor at time of the shooting, spoke publicly for the first time since the incident, reading a roughly 22-minute statement in which he took responsibility and apologized to each of the victims.

“I killed their innocence. I killed their ambitions. And I killed their sense of security. I not only physically killed people, I mentally killed people too. I don’t know how to describe the sorrow I feel when I think of the victims,” McKinney said. “The horror I caused is truly too much for anyone to bear.”

Multiple students were wounded during the shooting. Kendrick Castillo, an 18-year-old who confronted the gunmen in an effort to stop them, was killed. According to an arrest affidavit, McKinney told investigators he wanted to target students who “always made fun of him, ‘hated him,’ called him names and said he was disgusting for trying to be a guy.”

“I don’t deserve leniency, nor forgiveness. I don’t want a lighter sentence,” McKinney continued. He also had a message for would-be school shooters, urging potential copycats to get help: “The amount of pain it causes to everyone who ever cared about you, and innocent people, outweighs anything you are going through right now. Why would you idolize someone who hurt people, someone who was so weak that they couldn’t get help?”

John Castillo spoke about losing his son, and while looking at a televideo screen called McKinney pure evil to his face. As the suspect openly sobbed, Castillo condemned him to hell.

“This killer is a monster. You sit there with crocodile tears down your face? Well scripted,” Castillo said, crying. “I need to tell you something: These are real tears.”

Castillo added that he would never forgive McKinney for his actions and vowed to “fight him to the end.”

“You’ve awakened an activist who fights for safe schools,” he said.

Maria Castillo said her son was murdered with only three days left in the school year, a few days before Mother’s Day.

“I’m still waiting for him to come home,” she sobbed. “This evil killer destroyed my family.”

During his statement, McKinney addressed the Castillos.

“I want to start with an apology, but I never expect you to forgive it. Because what I’ve done is unforgivable,” McKinney said.

In February, McKinney pleaded guilty to multiple charges — first-degree murder, attempted murder and conspiracy to commit first-degree murder after deliberation.

“Your honor, I stand behind my guilty plea,” McKinney told Judge Jeffrey Holmes, appearing in the courtroom video conference.

McKinney openly sobbed throughout the hearing as he listened to witnesses recall the horror of that day, describing lasting traumas that have changed their lives forever.

“The pain he has inflicted will continue for many years,” said Yuritza Ojeda-Ayala. Her son, Gerardo Montoya Ojeda, was shot in the head and survived, but she said he no longer feels safe in any classroom. “He lost that sparkle that he had.”

Gabriela Leddy, a language arts teacher, shared an anguished account of that day.

“As we huddled in fear, my mind became imprinted with the faces of my students,” Leddy said through tears. “They were so brave. I am honored by their bravery.”

Leddy described the moment she started to run from the building, stopping when she saw Castillo’s body on the ground, his head covered by a bright green cloth.

“That moment of anxiety and fear of what was happening around me came to a halt,” she said. “Something compelled me to pause and say a quiet goodbye to this man.”

Leddy said she felt betrayed that a student who was one of her favorites was capable of such evil.

“I went above and beyond to try to foster an environment where Alec could feel safe and accepted,” Leddy said. “This is a heartless attack that spit in the face of the kindness that teachers like me, and other caring adults, showed him.”

Erickson has pleaded not guilty. He’s next due in court on Aug. 17, with his trial likely to begin in September, prosecutors said.

Investigators said that on the day of the shooting, McKinney and Erickson went to Erickson’s home and used an ax and a crowbar to pry open a safe containing handguns and a rifle. They then returned to the school with the handguns hidden in a backpack and the rifle inside a guitar case.

Student Nui Giasolli called McKinney, whom she once considered a close friend, a coward who projected his problems onto others.

“He made himself the judge, jury and executioner,” Giasolli said. “He’s not crying because he truly regrets it. He’s crying because he got caught.”

Morgan McKinney also testified at Friday’s hearing, saying her son has shown remorse and is getting mental health treatment.

“I tried to raise my children to be nothing but better people in our world,” she said. “I certainly am sorry for this tragic tragedy, and what it has caused you and so many others.”

Jennifer Krause’s son, Mitchell, was shot and survived.

“School shootings have to stop,” Krause said. “We can no longer mop the halls of our schools with our children’s blood.”

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