They said the boy's mother, Juanita Kinzie, is being held for investigation of first-degree murder.

The boy's uncle, Cogee Fields, said extended family members last saw Pacheco alive in January 2011.

He said the boy’s aunt, Yolanda Kinzie-Graber, became Pacheco’s guardian when his mother couldn’t take care of him.

But Juanita Kinzie soon asked for him back.

“Yolanda didn’t want to relinquish guardianship,” Fields said. “Social Services said she did have to turn him over to my sister. He was never seen again.”

Fields said they asked Juanita Kinzie about the boy’s whereabouts several times but she didn’t respond.

On Jan. 17, 2012, the family created a Facebook page to get the community to help find him.

One of the first posts, written in Caleb's voice, said, "The reason my family has started this page is they need help in finding me. I was last seen in mid-January 2011 with my mother leaving my aunt's home. That was the last time my family has seen me.

"There is not an AMBER ALERT for me at this time as the local authorities have to make contact with my mother and father to verify I am missing. My mother is not responding in an effort to help in finding me, therefore it slows the process down. So my family is reaching out to the community for help with sightings and the whereabouts of me."

Fields said the family contacted police a year ago, but was told there was no reason to suspect foul play. Family members said they tried contacting Social Services in three counties to ask for a welfare check but because authorities didn't know Kinzie's whereabouts, they couldn't do a welfare check without an address.

Family members said Caleb's mother moved around a lot.

They said they contacted the Logan County Sheriff's Office again last week, and deputies executed a search warrant at a mobile home where Caleb's family used to live before they moved out about six months ago. That's where they found the body.

"He was found underneath the trailer," Fields told 7NEWS. "He wasn’t buried. He was wrapped in a blanket with a few other items that (investigators) didn’t disclose."

Late Monday, the sheriff’s office sent out a news release, which stated in part:

"Preliminary identification of that child has identified him as Caleb Pacheco, DOB 7/15/08. The autopsy of the body was conducted on 1/23/12, with final autopsy results expected at a later date."

Fields said he was told that the remains were skeletal.

"So he’s probably been dead for a while," the uncle said.

A neighbor told 7NEWS he last saw the boy a few weeks before the family moved out.

When asked when that was, the neighbor said, "Last summer. It was warm out."

Fields said he doesn’t know what to think about Juanita.

"She’s my sister," he said. "This is not the sister I raised and protected. We worked together to raise two siblings. This isn’t her. I don’t know what happened."

Fields said Juanita Kinzie became involved in drugs several years ago.

"Methamphetamine is probably the key drug involved," he said.

Sean York, the father of one of Caleb’s sisters, told 7NEWS that family members are angry about a breakdown in the system.

"Who could sit there and let a little kid like that be missing for a whole year without doing (expletive?)"

Human Service officials called the boy’s death tragic, and said they couldn’t comment beyond that.

The sheriff’s office said a gag order has now been issued in the case.

7NEWS found that Kinzie has a prior criminal history, including arrests for domestic violence, violating a protection order, car burglary, damaging property and possession of burglary tools, according to a state arrest database.

In 2006, Kinzie pleaded guilty to domestic violence and harassment in Logan County and was given a deferred sentence of 18 months probation, according to court records.

But that sentence was revoked when she violated a protection order in March 2007, and she was sentenced to two months in jail, court records said. She also pleaded guilty to violating the protection order and was sentenced to three months in jail, 48 hours of community service and two years unsupervised probation.

In August 2011, Kinzie was arrested in Lakewood on charges of auto burglary, possession of burglary tools and damaging property, court records said. In June 2010, she pleaded guilty in Denver to false reporting on a mortgage loan transaction and was sentenced to 40 days in jail.