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'I remember aiming toward people and the floor': Second suspect in STEM school shooting testifies

Alec McKinney pleaded guilty last year in connection with the May 2019 shooting. He testified against his co-defendant.

DOUGLAS COUNTY, Colo. — The teen who previously pleaded guilty to charges in connection with the May 2019 shooting at STEM School Highlands Ranch testified at the trial for his co-defendant. He described details about the day of the attack and said the plan was for him to take the blame and that he was not expected to survive.

Alec McKinney was one of the last witnesses for the prosecution in the case against Devon Erickson, who was 18 at the time of the shooting. 

The two are accused in connection with the May 7, 2019 shooting that killed senior Kendrick Castillo and wounded several other students.

"To hear that kind of testimony is heart-wrenching," Kendrick's father John Castillo said. "It's the worst. It's the most evil that anyone can imagine."

RELATED: Witness: Kendrick Castillo didn't hesitate when he realized there was a shooter

At the trial, students testified that Castillo was the first person to lunge at Erickson when he appeared in their classroom with a gun. He was shot and died from his injuries.

Credit: Family friend
Kendrick Castillo

McKinney began his testimony around 4 p.m. Tuesday and returned to the witness stand Wednesday as the prosecution wraps up its case.

He testified about the morning of the shooting and said that he and Erickson met up in the school parking lot around 7 a.m. and left to go to Erickson’s house, where they did cocaine and then returned to school.

Around lunchtime, the two left the school again, McKinney testified, and went to McKinney’s house. Once there, he said they snorted more cocaine in the basement, according to McKinney.

He said earlier in the morning that Erickson had conversations with his girlfriend named Sophie and that Erickson felt he had “lost” her. McKinney testified that was kind of a pushing point to move forward with their plan to attack the school.

McKinney testified he looked for the key to a gun safe that was in the closet of a bedroom inside Erickson’s home. Ultimately the keys were not located, McKinney said.

Erickson retrieved an ax and crowbar from the garage, McKinney said, and the two of them knocked over the safe and then spent about an hour using the ax and crowbar to break it open.

Credit: KUSA
The gun safe on the floor of a closet inside the home of Devon Erickson.

He said four weapons and ammunition were inside. This included a rifle and three handguns. McKinney testified that two of the guns were later brought inside the school inside his backpack and that he had filled his pockets with ammunition. The rifle and the other gun and more ammunition were carried inside by Erickson inside a guitar case, he testified.

Prior to heading back to the school, McKinney detailed how Erickson asked him to retrieve a box of sharpies at his home. He said Erickson used them to write on his face and asked McKinney to write “God” on his chest, which he did.

McKinney also testified about writing that was on a wall inside the home that was done in red polish. It said, “the voices win.” According to an earlier transcript of an interview on the day of the shooting, McKinney said he wrote it, but in court said it was actually Erickson.

McKinney explained that a “majority” of the things he said during that May 7 interview were not true, because he said at that time, he was sticking to their plan that he would take the blame for the shooting.

He also explained how Erickson wrote “[expletive] society” in spray paint on his mother’s car in the garage of the home and said he poured gas on the vehicle and that Erickson set the vehicle on fire.

“The car kind of went up in flames,” he said. “There was a loud explosion.”

McKinney testified that Erickson was close enough to the vehicle that his hair was singed by the flames.

They then left the house and made their way back to the school. When they left, McKinney said he saw no visible flames coming from the car. Photos of the car shown in court don’t show any fire damage, but the fire was set on the side driver’s side of the vehicle which could not be seen in the photo.

As McKinney testified about what happened at the school, short video clips were shown of both and he and Erickson at the school. The first showed them walking up to the middle school entrance from the parking lot. McKinney testified Tuesday that this entrance was easier because they simply needed to get buzzed inside and wouldn’t get checked.

Credit: KUSA
A still of video showing the STEM shooting suspect in the school lobby before being buzzed inside.

A video was shown of them getting buzzed through the doors and inside the school. A third video shows them appearing to fist bump in the hallway before they go separate ways.

“We did a handshake we normally do,” McKinney said.

Credit: KUSA
The two suspects meet for the handshake before parting ways down opposite hallways.

When asked why they split up, McKinney responded, “to enter the classroom from different sides.”

He said he entered the classroom from one door and he recalled the teacher asked what he needed because it wasn’t his class. He said he told the teacher he needed to talk to Aaron.

McKinney said he did that because Aaron was someone the did want to get hurt in the shooting. He testified that Erickson entered through the other door and set down the guitar case near the back of the room. He said he saw Erickson talk to the teacher and then leave with another student. He testified that he was not sure why Erickson left but texted him and learned he was in the office.

McKinney said he left the backpack in the room and went to the office to check on Erickson but couldn’t get in there. Security video shows him standing in the hall for several minutes before Erickson comes out and enters the hallway.

Erickson eventually comes out and the two head back toward classroom 107. When asked if they talked, McKinney said he couldn’t remember.  However, according to a prior transcript from the day of the shooting, McKinney reported that Erickson said “let's go.”

When asked what he took that to mean, McKinney replied, “to go back to Miss Harper’s class and execute the plan.”

Just before the shooting began, McKinney said he texted Sophie and Bella and was telling them he was sorry and that he loved them.

McKinney fought back tears as he testified how Erickson picked up the guitar case and moved toward the back door. He said that Erickson slid up a magnet on the door and closed it. McKinney explained during Tuesday’s testimony that doing so would lock the door from the outside, preventing anyone from entering to help.

He said, Erickson then opened the guitar case. He recalled that the room was dark because the class was watching a movie. He testified that he was blocking one door and Erickson was at the other door and that were no other exits to the classroom.

McKinney testified that Erickson pulled a gun from the guitar case and said nobody move.

"I went to my backpack and I pulled one [a gun] out too," McKinney said.

He said he recalled a lot of movement and then a few kids got up and rushed toward Erickson, around the same time he said he heard gunshots. He began firing too from the other side of the room, he testified.

“I remember aiming toward people and the floor,” he said. When asked what his goal was, he said, “to shoot them.”

He said he shot a total of nine times because that was the number of bullets that were in the weapon. He said he was shooting aimlessly at people he saw moving and tried to continue firing even after he was out of bullets but the gun just clicked. He said eventually someone climbed over a desk and tackled him.

"It’s difficult but there’s a part of it that is almost, I don’t know enlightening that he’s divulging so much information," John Castillo said.  

The director of IT at the school heard the commotion in the hallway and was able to get to the gun from McKinney. The other gun was still inside his backpack in the classroom and McKinney went back inside to get it. He then came out in the hallway and pointed the gun to his head, but did not pull the trigger.

Shortly after, he was confronted by the school security guard in the hallway and was ordered to the ground and handcuffed.

McKinney also testified about several two Snapchat videos made the day of the shooting. He said they were “staged” to make it look like he (McKinney) was to blame for the shooting. One he said shows him acting like he’s forcing Erickson to open the gun safe. He said they recorded that video three times before it was “convincing enough” but deleted their two prior video attempts.

Shortly before lunch, the defense team began its cross-examination of McKinney, where they harped on McKinney's story changing from the day of the shooting. Attorney Julia Stancil noted that the version of events he told in court didn't come up until nine months after the shooting during an interview with prosecutors.

"So, 9 months into your incarceration, you just suddenly don’t have voices in your head anymore," Stancil asked.

"It was 9 months of me being sober yes," McKinney replied.

She suggested that he was changing his story in order to take advantage of a special program that could grant him early release.

The program applies to certain offenders convicted as adults for crimes committed when they were juveniles but those with serious mental health issues are not eligible.

On Tuesday, he described how he and Erickson did drugs together and discussed carrying out the attack in the weeks just prior to the shooting.

McKinney appeared on the witness stand in an orange jumpsuit and was shackled. He said that he and Erickson were friends prior to the shooting and their friendship started in January 2019.

RELATED: Opening statements given in trial of student accused of carrying out deadly attack at STEM School Highlands Ranch

In April, the month before the shooting, McKinney testified that they got into conversations on Snapchat about the most messed up thing on their bucket lists.

McKinney said he talked about wanting to do acid and testified that Erickson said he wanted to get away with killing someone.

He testified that Erickson had talked about throwing a party at a cabin and killing everyone who was there, but he said the conversation later turned to talk about carrying out the attack at the school instead.

McKinney testified that Erikson said classroom 107, where the shooting took place, was the "ideal place" to carry out the attack because it was where the most people he hated would be at the same time.

He testified that there were also people in the classroom that they didn't want to hurt.

McKinney said that the plan that day was that he was going to die. When asked how he was going to die, he said that the plan was for Erickson to kill him, after killing everyone in the classroom.

"Hearing the fact their intentions were to murder everybody in that classroom, definitively, without sparing a single life and execution-style, that was a hard thing," John Castillo said.  

McKinney said the two had discussed blaming the shooting on him.

RELATED: 'How the hell am I going to get out of here': Former STEM student describes shooting inside her classroom

Opening statements for the trial of Erickson began on May 27. Since then, the prosecution has been laying out its case against him.

McKinney pleaded guilty in February of last year 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

He was sentenced to life in prison but will be eligible for parole after 40 years due to his age at the time of the crime.

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