(FOX NEWS) -- A Colorado teen convicted in the metal-pipe beating death of a 10-year-old girl was sentenced to life in prison Tuesday.
Aidan Zellmer, now 17, was tried as an adult. He ultimately pleaded guilty, as part of a plea deal, to one count of first-degree murder in the death of Kiaya Campbell on June 7, 2017. He could become eligible for parole after 40 years, authorities said.
“In 27 years as a prosecutor, I have never seen a 15-year-old commit such a violent act,” 17th Judicial District Attorney Dave Young said at the sentencing, according to FOX 31 Denver.
After slugging the child in the head five times with the pipe, Zellmer then dragged her into a ditch, where he left her to die, an affidavit showed.
Kiaya suffered blunt-force injuries to the head as well as wounds to several fingers, according to an autopsy report. Officers used blood and DNA evidence collected from Zellmer's shoes to link him to the murder, the station reported.
Kiaya's body was found naked from the waist down and, while there was evidence of a sexual assault, sex crime charges were later dismissed as part of the plea deal, per FOX 31.
Zellmer and Campbell had left their home in Thornton to steal Pokemon cards and candy, according to the affidavit.
The station reported that Zellmer's mother was in a relationship with Campbell's father at the time.
A motive for the crime has yet to be established, the Denver Post reported.
Zellmer’s defense attorney spoke to the teen’s history with mental health issues and a troubled family life marked by abuse, per the report.
Young dismissed Zellmer’s past as an excuse for the murder, the Post reported.
According to Chantel Campbell, the victim's mother, 40 years is not enough.
“No mother should have to hear about how her daughter was brutally beaten,” she said.
Zellmer will not be placed with adults in the Department of Corrections until he turns 18, the Post reported.