A former high school student convicted of killing a teenager and injuring eight others at a Denver-area school in 2019 has been sentenced to life in prison without parole.

A toxicologist testified Friday that one of the suspects in a fatal shooting at a suburban Denver high school in 2019 was such a chronic drug user that he couldn't understand the events around him.

A prosecutor says a teen accused of killing a fellow student at his suburban Denver school in 2019 agreed to participate in the attack as long as it looked like he was pressured into participating.

McKinney, 17, is the younger of the two students charged in the May 7, 2019, shooting. The minimum sentence for first-degree murder for a juvenile is life in prison with the possibility of parole after 40 years while the minimum sentence for an adult is life without the possibility of parole. Erickson, 19, has pleaded not guilty to all the same charges McKinney originally faced in the shooting. His lawyers have portrayed McKinney as the ringleader who pressured Erickson to participate. Colorado became the 22nd state to abolish the death penalty this year but Erickson could have still been eligible for it because the shooting happened before that law was passed.

CNN videoDENVER - One of the teenagers who allegedly opened fire at a Colorado charter school in May said he accidentally fired just one shot when classmates rushed him. But prosecutors said Wednesday that he fired more shots, and only stopped because his gun jammed. District Attorney George Brauchler said Wednesday that Erickson's handgun jammed when one of the casings did not eject properly. Following the shooting, Erickson told investigators that suspect Alec McKinney made him do it and tasked him with guarding an exit and telling everyone not to move. The two students used the middle school entrance because they knew they would be able to get the guns into the school, the affidavit states.

Devon Erickson told detectives he was forced to take part in the attack on his high school. The-CNN-Wire & 2019 Cable News Network, Inc., a Time Warner Company. All rights reserved.

In the message, McKinney allegedly told him not to come to school. The two suspects are accused of carrying out a mass shooting at STEM School Highlands Ranch near Denver in May, killing Kendrick Ray Castillo, 18, and wounding eight others. Following the shooting, Erickson told investigators that McKinney made him do it and tasked him with guarding an exit and telling everyone not to move. Erickson took the two handguns used in the shooting from his parents, according to a law enforcement source. The two students used the middle school entrance because they knew they would be able to get the guns into the school, the affidavit states.