Sixteen-year-old Alec McKinney and eighteen-year-old Devon Erickson were convicted on dozens of charges and sentenced to life imprisonment.

[7] A district official wrote a letter on December 19, 2018, urging the School Executive Director to investigate concerns to determine their legitimacy and to take any remedial action that may be appropriate.

[10][11][12] At 1:53 pm, Erickson and McKinney entered the school carrying handguns and other weapons hidden in a guitar case and a backpack.

[13][14] The school proceeded to announce a lockdown,[6] and the Douglas County Sheriff's Office issued a warning via Twitter to avoid the area, describing it as an "unstable situation".

[19] According to a student, Devon Erickson allegedly pulled out a gun from his guitar case and yelled, "nobody move".

[21] Simultaneously from the other side of the room, Alec McKinney raised a Taurus revolver and fired it until it was empty, hitting 4 students.

Not knowing that McKinney was the shooter, the teacher picked up the revolver before going inside the classroom to move Erickson's handgun as well.

They also went to Erickson's home and seized a car with hand-painted graffiti that read "Fuck society" as well as "666" and a pentagram.

[32] At least three students, 18-year-old seniors Kendrick Castillo, Joshua Jones, and Brendan Bialy, lunged at an attacker, later identified as Erickson.

[39][40] Local media outlets reported that the weapons used by the suspects were stolen from a parent, and that neither were known to law enforcement prior to the attack.

McKinney said he planned to target two students in particular as they had bullied and ridiculed him due to his gender identity and called him "disgusting".

McKinney said that "he wanted the kids at the school to experience bad things, have to suffer from the trauma like he has had to in his life."

McKinney also stated he has heard voices and has suffered from homicidal and suicidal thoughts since the age of 12, and refused to take medication so that he "wouldn't feel alone".

McKinney was charged as an adult—though his lawyers tried to move his case to the juvenile court, the judge denied the motion.

On the first degree murder charge, he faced a minimum sentence of 40 years to life in prison, but could be eligible for release earlier than that if he enters a rehabilitation program and earns time off for good behavior.

[59][60] In March 2020, the 18th Judicial District Attorney announced they would not be seeking the death penalty for Devon Erickson.

[65] President Donald Trump issued a statement on Twitter the day after the shooting, thanking first responders for "bravely intervening" and writing, "We are in close contact with law enforcement".

[66] White House Deputy Press Secretary Judd Deere issued a statement: "Our prayers are with the victims, family members, and all those affected" by the shooting, as did Republican Senator Cory Gardner: "The safety and comfort of our schools should never be taken away".

[69][70] A large portion of the students walked out of the event, which was organized by a local chapter of the Brady Campaign to Prevent Gun Violence.

[73] Another interviewed shortly after the vigil claimed, "I understand calling for gun control but like these were handguns — these aren't AR-15s these kids are carrying.