Kyron's Dad: I Think Stepmom Had Accomplice

Kyron Horman's father says he "firmly believes" someone in addition to Terri Horman was involved in Kyron's disappearance.

The 7 year old was last seen June 4 at his Oregon-area elementary school, and Terri is the also person known to have seen him alive. She's the now-estranged wife of Kyron's father, Kaine Horman.

Kaine and Desiree Young, Kyron's mother and Kaine's ex-wife, have publicly stated they think Terri had something to do with Kyron vanishing.

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Now, Kaine tells The Oregonian he's convinced Terri had a hand in whatever happened to his son.

In an e-mail interview with the newspaper, Kaine says, "Based upon briefings, I firmly believe that someone else is involved."

Police haven't named Terri a suspect or person of interest, but she remains the focus of the investigation, reports CBS News Correspondent Bill Whitaker.

Terri moved out of the Portland home she once shared with Kaine and their children after reaching a court settlement this weekend.

She was spotted Saturday in Roseburg, Oregon, where her family lives, Whitaker says, She was seen driving away with her father.

With Terri out of the house, Kaine moved back in. He left June 26 after learning from investigators that Terri allegedly had hired a landscaper to kill him. He also filed for divorce and obtained a restraining order against Terri.

According to court documents, Terri developed a "sexual relationship" with a high school friend of Kaine's.

In the documents, Kaine accuses Terri of attempting to kidnap the couple's 20- month old daughter from a local gym.

Over the weekend, Kyron's parents visited the school where the second-grader was last seen. The community has helped create a "wall of hope' in his honor.

"It's great to see everyone supporting Kyron," Kaine says. "That's why we're all here, to find him and it's very overwhelming for us to come here, in a good way."