Senior Kendrick Castillo was killed in the May 7 shooting. Eight other students were injured.

DOUGLAS COUNTY, Colo. — The 16-year-old suspect arrested in connection with last week's STEM School Highlands Ranch shooting that killed 18-year-old Kendrick Castillo and injured eight others has been charged as an adult with first-degree murder.

Maya McKinney, who goes by Alec, will remain in a juvenile detention facility and will not be eligible for the death penalty under Colorado law, according to the district attorney's office.

"The 16-year-old is charged with first-degree murder as an adult," District Attorney George Brauchler said. "And there are a bunch of other charges that did not come up in open court that I can't discuss."

According to court records, McKinney faces charges for:

First-degree murder after deliberation (1 count)

First-degree murder extreme indifference (1 count)

Conspiracy to commit first-degree murder after deliberation (1 count)

Attempted first-degree murder after deliberation (6 counts)

Attempted first-degree murder with extreme indifference (25 counts)

Second-degree arson with damage of $100 or more (1 count)

Conspiracy to commit second-degree arson with damage of $100 or more (1 count)

Third-degree burglary (1 count)

Conspiracy to commit third-degree burglary (1 count)

Theft ($2,000-$5,000) (1 count)

Conspiracy to commit theft ($2,000-$5,000) (1 count)

Weapon-possession on school grounds (1 count)

Criminal mischief ($1,000-$5,000) (1 count)

Conspiracy to commit criminal mischief ($1,000-$5,000) (1 count)

Handgun possession by a juvenile (1 count)

Interference with school staff (1 count)

Reckless endangerment (1 count)

Violent crime causing death/serious bodily injury (a sentencing enhancer)

Violent crime — weapon used (a sentencing enhancer)

According to Brauchler, the defense plans to request a reverse transfer hearing to move the case back to juvenile court. As of now, his next court appearance is set for June 14.

McKinney and the other suspect, Devon Erickson, 18, both remain in jail, where they're being held without bond.

Erickson was also in court Wednesday for the filing of similar charges. Defense attorneys acknowledged the complaint but waived any reading or advisement of the charges.

The judge denied a request from the defense to allow the suspect to be unshackled for the hearing. His next court date was set for June 7. According to court documents posted online Wednesday, he now faces 48 counts.

Erickson's charges include the following:

First-degree murder after deliberation (1 count)

First-degree murder extreme indifference (1 count)

First-degree murder after deliberation conspiracy (1 count)

Attempted first-degree murder after deliberation (6 counts)

Attempted murder extreme Indifference (25 counts)

Second-degree arson damage $100 or more (1 count)

Handgun-providing/permitting juvenile to possess (1 count)

Third-degree burglary (1 count)

Second-degree arson damage $100 or more-conspiracy (1 count)

Possession of a weapon on school grounds (1 count)

Criminal mischief $1000-$5000 (1 count)

Criminal mischief-$1000-$5000 conspiracy (1 count)

Theft $2,000-$5,000 (1 count)

Theft $2,000-$5,000 conspiracy (1 count)

Third-degree burglary conspiracy (1 count)

Interference with school (1 count)

Reckless endangerment (1 count)

Violent crime-causing death or serious bodily injury (a sentence enhancer)

Violent crime-weapons used (a sentence enhancer)

He could face the death penalty, although Brauchler said he had done "no analysis of that issue at all."

Ahead of Wednesday's hearing, he was being held on one count of suspicion of first-degree murder after deliberation and 29 counts of attempted first-degree murder after deliberation.

The pair is accused of opening fire at two different locations inside STEM School Highlands Ranch just after 1:50 p.m. on May 7.

Castillo, 18, was killed in the shooting when fellow students said he lunged at the suspect who had entered their classroom.

His parents, John and Maria Castillo, attended the hearings for both suspects, despite having a celebration of life for their son Wednesday afternoon.

"It would have easy for them to say, 'I'm not going to make it to court today, because in less than two hours, we're about to have a memorial service for our son,'" Brauchler said. "From the word go, they have made it clear, 'Our intention is to be here for every single hearing,' and today I think is a good example of that."

“I’m going to have a lot of guilt for a long time by raising a good individual...his actions are heroic, but the consequences are steep," Kendrick's father John Castillo said.

Eight other students were shot and wounded. They have all been released from the hospital.

Brendan Bialy and Joshua Jones also helped subdue one of the gunmen at the school, according to classmates.

"We rushed him," Jones said on Tuesday. "I pulled him to the ground, Brendan got the gun, Kendrick shoved him against the wall first off."