THORNTON, Colo. (CBS4) – The arrest of the 15-year-old boy in the murder of 10-year-old Kiaya Campbell came as an “utter shock” to the mother of the boy’s close friend.

Kiaya Campbell (credit: CBS)

Aidan Zellmer (credit: CBS)

Campbell was killed in Thornton last week and Aidan Zellmer was arrested two days later. The two juveniles’ parents were dating.

Zellmer is so young that prosecutors need a judge’s permission to charge him as an adult. He currently faces two first degree murder charges.

Crystal Gabaldon’s 15-year-old daughter was best friends with Zellmer. She said she watched television newscasts to get updates on the Campbell case and used it as a warning to her children.

(credit: CBS)

“Because you know I have girls that age. I go ‘Look at what can happen, you guys. You never know what can happen. You guys have got to be careful.’ A couple of days later that’s when I seen that Aiden was a suspect. And I was just in utter shock,” Gabaldon said.

Aidan Zellmer is seen with Crystal Gabaldon’s daughter. (credit: CBS)

Gabaldon said her daughter and Zellmer have known each other for five years.

“Nothing ever would make me think that he would do something, even to hurt my kids. I would trust him completely around my girls at that,” she said.

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Gabaldon told CBS4 she believes Zellmer is innocent.

“I honestly deep down in my heart don’t feel like Aidan could have did something like that. He is just … so sweet,” she said.

Zellmer is being held without bond. It could be several weeks until prosecutors will be able to proceed with their case.