Devon Erickson (centre) accused of taking part in a deadly school shooting in Colorado. File Photo/Reuters

Two teenagers accused of fatally shooting a classmate and wounding eight others at a Denver-area high school last week are set to return to court on Wednesday for the formal filing of charges.

Devon Erickson, 18, and Alec McKinney, 16, who was listed on the court docket by the name Maya Elizabeth McKinney but who identifies as male, were both arrested on suspicion of a single count of first-degree murder and 29 counts of attempted murder immediately after the May 7 shooting spree.

The pair is accused of opening fire on fellow students inside two classrooms at the Science, Technology, Engineering and Math (STEM) charter school in Highlands Ranch, about 25 miles south of Denver.

The two teens made their initial court appearances last week in separate hearings before Douglas County District Judge Theresa Slade, who ordered them both held without bond.

Denver’s ABC affiliate television station has reported that the two pistols used in the attack were stolen from the home of Erickson, whose parents had purchased the guns legally. Court documents relating to the case have been sealed. The Douglas County Sheriff's Office has declined to comment.

District Attorney George Brauchler said last week that he would reveal at Wednesday’s proceeding whether he will charge McKinney as a juvenile or an adult.

Slain student Kendrick Castillo is to be honored a memorial service on Wednesday at a Highlands Ranch church. The 18-year-old robotics enthusiast and aspiring engineer was shot dead as he and two other students charged at the shooters in an effort to disarm them.

Just three days shy of graduation, Castillo was pronounced dead at the scene, Douglas County Sheriff Tony Spurlock told Reuters.

The attack occurred less than a month after the 20th anniversary of the Columbine High School massacre in nearby Littleton, in which two students shot 13 people to death before committing suicide.

Reuters