Shackled at the waist with his hair dyed purple, Devon Erickson — one of the Colorado STEM school shooting suspects — made his first court appearance Wednesday, in which spoke only once and kept his head hung low the entire time.

The 18-year-old is accused of opening fire inside the Denver-area institution, where on Tuesday he killed one student and wounded eight others, with help from one of their underage female classmates.

The girl, who is reportedly transitioning from female to male, has not been identified. She did not appear in court Wednesday as authorities are still determining whether to charge her as an adult.

She and Erickson allegedly entered the STEM school in Highlands Ranch and used two pistols to take out their victims.

Police have yet to release a motive, but sources told Denver7 that it went “beyond bullying” and involved “revenge and anger towards others at the school.” They said one of the shooting suspects was involved in legal and illegal drug use and was currently in therapy, though it’s unclear which one.

Erickson was held without bond Wednesday pending his next court appearance. His formal charges hearing is set for Friday afternoon.

This week’s rampage is the first school shooting since Columbine to involve two alleged gunmen. Investigators said they were looking “deep” into the suspects’ social media accounts, phones and computers to try to obtain more information about them.

Officials have confirmed that a car was seen leaving Erickson’s home Tuesday night with graffiti spray-painted on it that read, “F–k society.” They wouldn’t say, though, whether he was driving it.

Erickson nodded and said “No” just once while answering questions during his court appearance. He was booked on 30 counts, including first-degree murder.

“Our hearts are hurting for them,” said Colorado Gov. Jared Polis at a media briefing Wednesday, recalling how he felt “sick” after hearing about the shooting.

“This does not define us,” added 18th Judicial District Attorney George Brauchler. “It won’t today and it won’t tomorrow.”