MORGAN COUNTY, Colo. (KDVR) — A teenager was arrested on a count of first-degree murder in the death of a 15-year-old girl who went missing over the summer.

The remains of Shree Leann Emmons-Henderson, who also went by Alex, were found two days after she was reported missing on July 5, according to the Morgan County Sheriff’s Office. An autopsy found she died from a single gunshot wound.

Her remains were not identified until Monday, the Sheriff’s Office said.

On Wednesday, investigators arrested a 16-year-old boy in Brighton, the Sheriff’s Office said. The teen’s name was not released, but he is expected to be tried as an adult.

The teenager is being held in a juvenile detention center on a $1 million bond.