Thornton Police have arrested a 15-year-old in connection to the death of 10-year-old Kiaya Campbell.

Police say they arrested the male, who has not been identified, on Saturday at 11:38 p.m. He was transported to the Adams County Juvenile Detention facility for investigation of first-degree murder.

Campbell was first reported missing on Wednesday night. An Amber Alert was issued around 1:30 p.m. the next day.

A resident who joined the search for Campbell found her body around 5:30 p.m. on Thursday in the area of 128th Avenue and Jasmine Court – about two miles from where Campbell was last seen.

RELATED: Coroner IDs body as missing girl, police deem it homicide

She and the 15-year-old son of her father’s girlfriend were walking from his home to a shopping center in the area of 136th Avenue and Colorado Boulevard when the pair allegedly became separated during a rainstorm.

Neighbors told 9NEWS they do not believe it was raining at the time.

Campbell was first reported missing by her sister just before midnight.

Campbell lives with her mother in Montbello and was not familiar with the area near her father’s Thornton home.

Authorities have not said if the 15-year-old in custody is the same teen who was with Campbell before she went missing.

It's unclear at this time if the district attorney will ask the teen -- who has not been formally charged yet -- be charged as an adult. If the district attorney does, the court then takes into account the maturity of the suspect, the severity of the crime, the manner in which it was committed and other factors.

9NEWS legal analyst Scott Robinson said for charges like this, someone under 18 at the time of the crime cannot be sentenced to life without parole. The death penalty is also not an option.

The most severe punishment the teen could receive if convicted, Robinson says, could be a life sentence with the possibility of parole after 40 years.

It typically takes several months before a decision like this is made.

“Any time a 10-year-old is murdered, it doesn’t matter if the preparator is 15 or 50; it’s a heinous crime,” Robinson said.

Community members held a candlelight vigil for Campbell on Saturday night near where her body was found.

RELATED: Candlight vigil held for 10-year-old girl found dead in Thornton