Kyron Horman update: Desiree Young, believes son is dead, stepmom is responsible

(CBS/KOIN) ROSEBURG, Ore. - Desiree Young's heart is telling her to hold on to hope that her son, Kyron Horman, will come home safe and sound, but her brain tells her to prepare for the worst.

For the first time since her son vanished more than eight months ago, Desiree Young conceded that Kyron is probably dead.

PICTURES: Kyron Horman Missing

That's what Desiree Young told NBC station KOBI Saturday, as she pressed her campaign to pressure Kyron's step-mother into cooperating with police.

Young took that campaign to Terri Moulton Horman's neighborhood in Roseburg, Ore. She and her husband, Tony Young, along with several supporters, handed out fliers to Terri's neighbors, asking them to question Terri about Kyron's disappearance.

Kyron Horman disappeared from Portland's Skyline School on June 4, 2010. Terri Horman, his step-mother, is the last person known to have seen Kyron alive. During the initial phases of the investigation, Desiree - Kyron's biological mother - was sometimes seen with Terri, as the two women appeared to console each other.

But as law officers followed clues, interviewed witnesses, studied cell phone records and looked into family backgrounds, suspicion increasingly fell on Terri. Kyron's father, Kaine Horman, filed for divorce from her. Terri left their Skyline-area home and moved into her parents' Roseburg home.

Meanwhile, Desiree became increasingly skeptical of Terri's denial of guilt, as her public accusations about Terri's activities became more pointed and accusing. This weekend, practically in Terri's back yard, she made it clear that she was there to put pressure on her to provide the information necessary to bring closure, according to CBS affiliate KOIN. In her most direct accusation to date, she declared, "We know that Terri is responsible, yet she remains silent."

But she also said, for the first time, that she believes Kyron is dead. As recently as February 14, she released an open Valentine's Day message to Kyron, saying "God is looking over you and protecting you until I get there, so be brave, I am coming." She added that "I know that we are getting closer every day, I dream about finding you and I know they will bring you home."

Despite that statement, Desiree has appeared increasingly resigned to the idea that she may never see her son alive again.

One way or the other, Desiree Young is seeking closure. She clearly believes that Terri Horman can provide that closure to her and to everyone else involved in the case.

To date, Terri Moulton Horman has not been legally accused of any crime.