Kyron Horman Update: Missing Boy's Father Claims Stepmom is "Severely Emotionally Disturbed"

PORTLAND, Ore. (CBS/KOIN) The father of Kyron Horman, the Portland-area boy who mysteriously vanished nearly five months ago, has argued in newly filed court papers that his estranged wife is "severely emotionally disturbed" and should not have custody of their 23-month-old daughter.

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Kaine Horman alleged in court documents filed Monday Terri Horman is an alcoholic who suffers from an "undiagnosed personality disorder" and that giving her custody of their daughter, Kiara, could endanger the child.

He said he fears his daughter may have witnessed an "unimaginable act of horror," according to CBS affiliate KOIN.

Terri Horman was the last person to report seeing 8-year-old Kyron walking toward his second grade classroom after a school science fair June 4. She has not been named a person of interest or suspect in the boy's disappearance.

Kaine Horman once again said he believes his wife is responsible for his son's disappearance and cannot be trusted near their daughter.

"Her actions are horrifying and unexplainable. Kiara's physical and emotional safety are now at extreme risk," he said.

In July he claimed that Terri Horman suffered from postpartum depression following Kiara's birth.

Also included in the documents are over 20 pages of sexually explicit text messages between Terri Horman and Michael Cook, a high school friend of Kaine Horman, supposedly sent less than one month after Kyron disappeared, reports KOIN.

The messages also mention the use of a "clean phone" to avoid monitoring; and in one instance Terri allegedly asks Cook to deny that she visited him.

Kaine Horman claimed it was common to see Terri passed out on the couch after drinking, which affected their daughter's sleeping pattern, reports KOIN. He also described Terri as too concerned with her looks and her social media life, calling the amount of time she spent online "unhealthy."

Prior to these most recent filings, Kaine Horman filed for divorce and filed a restraining order against Terri Horman after police said she tried to hire a landscaper to kill him in December 2009.

COMPLETE COVERAGE OF KYRON HORMAN ON CRIMESIDER