Watch CBSN Live

Kyron Horman's Mom to Stepmom: Come Clean

The biological parents of an Oregon second-grader missing nearly a month pleaded Thursday for his stepmother to cooperate with authorities.

"We implore Terri Horman to fully cooperate with the investigators to bring Kyron home," the boy's mother, Desiree Young, said with her voice cracking, reading at a media briefing from a joint statement with his father, Kaine Horman.

Kyron Horman's Stepmom Hires Top Lawyer
Missing Oregon Boy's Father Files for Divorce
Investigators Focus on Kyron Horman's Stepmom
Kyron Horman's Case Now Considered Criminal

Terri Moulton Horman is the last person known to have seen 7-year-old Kyron Horman before he vanished on June 4. Investigators have not named her as a suspect or a person of interest in Kyron's disappearance but, says CBS News Correspondent John Blackstone, she's been the focus of the probe.

A call to her high-profile defense lawyer, Stephen Houze, was not immediately returned Thursday. She retained him this week.

The statement from Kyron's mother and father also said they're hopeful that 7-year-old Kyron Horman is still alive.

"Keep his face out there, keep looking for him," Young said. "We're optimistic Kyron will be found, and we can't comment beyond that."

She added that Kyron is allergic to bees and has a red birthmark on his forehead.

It was the family's first public statement asking Terri Horman to cooperate following a string of incidents that have appeared to isolate her from the family.

"Clearly," says former federal prosecutor Laurie Levenson, "there's been a division here, and the biological parents are pointing the finger at Terri Horman saying, 'What happened, you should be helping. You know." '

Police have given Terri Homan two polygraph tests.

"It's very surprising that it took so long for her to actually hire a lawyer; she's been in the spotlight and the target of this investigation for so long," Levenson added.

Kaine Horman filed for divorce Monday, citing "irreconcilable differences," and moved out of the home they shared. Also, a judge granted his request barring Terri Horman from contact with her children and access to firearms.

Terri Horman and her estranged husband also have a 19-month-old daughter, and she has a teenage son from a previous marriage. Kaine Horman took the toddler with him when he moved out.

Court documents showed Kaine Horman moved out of the family home last week.

Kyron disappeared after a science fair at Skyline Elementary School, which did not have an automatic notification system at the time. Terri Horman, who has raised Kyron since he was an infant, contacted the school when the boy didn't come home on his school bus on June 4. The sheriff's office declared the case a criminal investigation on June 14.

Search teams spent 10 days combing the hills and ravines near the school in one of the largest search operations in state history. The sheriff's office issued a flier to everyone who was in Skyline Elementary on June 4 that included two questionnaires - one directed at adults and another for children. Both asked if anyone saw Kyron or Terri Horman at or near the elementary school, or if they witnessed a pickup matching the description of the family's white Ford F250 pickup.

Terri Homan last appeared publicly at a news conference in early June with the boy's father, appealing for help in finding Kyron.