DENVER (AP) — 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.

Devon Erickson was sentenced Friday after victims and families gave emotional testimony about the lasting trauma from the shooting at STEM School Highlands Ranch.

Erickson, now 20, was convicted of partnering with another student in the attack on a classroom of high school seniors watching a movie.

Because he was 18 at the time of the shooting, Erickson faced a mandatory sentence.

One former student who helped stop the attack said Erickson killed their classmate and “didn’t care.”

CASTLE ROCK, Colo. (KMGH) — A jury on Tuesday found Devon Erickson guilty of 46 charges, including first-degree murder, in the 2019 STEM School Highlands Ranch shooting in Colorado, which left one student dead and others wounded.

The jury returned the verdicts about 1:30 p.m. after beginning deliberations Tuesday morning.

Erickson now faces a mandatory sentence of life in prison without the possibility of parole. His sentencing date has not yet been scheduled.

Erickson's charges included two sentence enhancers. Along with first-degree murder, the charges included attempted murder, conspiracy, burglary, and arson. Erickson was also charged with two misdemeanors.

Erickson's attorneys had argued that he was pressured into participating in the May 7, 2019 shooting by his fellow teen suspect, Alec McKinney, who last year pleaded guilty and received a sentence of life in prison.

But prosecutors said Erickson and McKinney were partners in a "shared scheme" to carry out the shooting, and McKinney — despite initially telling police that he had pressured Erickson — also testified that he and Erickson were equal partners in the shooting.

The prosecution in its closing argument Monday pointed to evidence that showed Erickson and McKinney had staged a Snapchat video in which McKinney was yelling at Erickson to open a gun safe at his home on the day of the shooting.

McKinney testified that the teens had filmed two prior versions of the video but did not think it would be believable.

Prosecutors also pointed to friendly Instagram messages between the teens and video that showed them giving each other a fist bump — evidence, according to the prosecution, that proved Erickson was going along with the plan to carry out a shooting.

Kendrick Castillo, a senior student at the school, died in the shooting. Castillo and several other students rushed Erickson and took him down, halting the shooting and saving other students' lives, officials have said.

Prosecutors throughout the trial called Castillo and the other students heroes.

This story originally reported by Ryan Osborne on TheDenverChannel.com.